A suffix which indicates that the word is the name of an enzyme, which is a type of protein that catalyzes biological or biochemical reactions. For example, "cellulase" or "polymerase".

2. -emia (adj.: -emic)
Definition:

A suffix indicating that the word has to do with the blood, a condition of the blood, a substance within the blood, etc. For example, anemia is the lack of sufficient functioning hemoglobin in the blood.

"-emic" is a suffix indicating that one is suffering from a condition of the blood.

3. -esis
Definition:

A suffix indicating that the word has to do with "action" or "process."

4. -ostomy
Definition:

A suffix meaning the creation of an opening, as in colostomy.

5. -partite
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

Divided, almost to the base, into segments (commonly applied to a style).

6. 1,4-glucan branching enzyme (brancher, branching enzyme, Q enzyme)
Definition:

An enzyme which makes new branches in glycogen or amylopectin molecules by moving a 1,4-D-glucan chain on the molecule to a primary hydroxyl group (an -OH group) on the same molecule.

7. 1-thiouridine
Definition:

A modified pyrimidine base formed by the replacement of an oxygen atom by a sulfur atom and is found only in tRNAs.

8. 100-year flood
Author:
Definition:

The magnitude of a flood expected to occur on the average every 100 years, based on historical data. The 100-year flood has a 1/100, or one percent, chance of occurring in any given year.

9. 12-O-tetradecanoylphorbol-13-acetate (TPA)
Definition:

A plant phorbol ester which promotes tumor formation by activating membrane protein kinase C.

10. 16S rRNA
Author: Mirrored from Tsute Chen's Glossary of Microbiology
Definition:

A large polynucleotide (about 1500 bases) which functions as a part of the small subunit of the ribosome of prokaryotes and from whose sequence evolutionary information can be obtained; the eukaryotic counterpart is 18S rRNA.

11. 2-aminopurine
Definition:

A derivative of purine which can substitute for adenine during DNA replication. As a result, it can induce mistakes in DNA and is therefore a powerful mutagen.

12. 3' end
Definition:

The end of a nucleic acid that doesn't have a nucleotide bound to its 3' of the terminal residue.

13. 3'-azido-3'-deoxythymidine (AZT)
Definition:

An antibiotic used to treat infection by HIV (the AIDS virus). The drug works by blocking replication of the HIV genetic material (in this case it is composed of RNA rather than DNA) by preventing the viral RNA from inserting into the host DNA.

14. 5' end
Definition:

The end of a nucleic acid sequence where the 5' position of the terminal residue isn't bound by a nucleotide.

15. 5-fluorodeoxyuridine
Definition:

An anti-cancer agent derived from 5-fluorouracil which forms in cells that have been treated by 5-fluorouracil.

16. 5-fluorouracil (5-FU)
Definition:

An anti-cancer agent similar in structure to the nitrogenous base thymine, which inhibits the enzyme dihydrofolate reductase (DHFR) and thus nucleotide synthesis, so that it is particularly harmful to rapidly growing cells such as in tumors.

17. 5-hydroxymethylcytosine
Definition:

A nucleotide base derived from cytosine which is used by the bacteriophage T4 in place of cytosine in its DNA. The substitution protects the bacteriophage from its own nuclease enzymes (enzymes which cut apart DNA).

18. 5-methylcytosine (5MeC)
Definition:

This is the methylated form of cytosine (a nitrogenous base in nucleic acids); i.e., a methyl group has been added to the cytosine molecule.

19. 6-aminopenicillic acid
Definition:

A chemical structure found as the common core for all of the penicillins. The different penicillins are distinguished from one another by having a variable side group

20. 6-mercaptopurine
Definition:

A toxic drug used to treat acute forms of leukemia (lymphocitic and granulocytic) by inhibiting DNA synthesis.

21. 6-mercaptopurine
Definition:

Purine analog which can result in DNA damage upon incorporation during synthesis of a DNA strand.

22. 6-thioguanine
Definition:

Purine base analog which hypozanthine-guanine phosphoribosyl transferase (HGPRT) transforms into a toxin.

23. 7-methyl guanosine
Definition:

A guanosine ribonucleotide (has the nitrogenous base guanine attached to the sugar ribose) which has a methyl group attached to the 7th ring atom of the guanine (a nitrogen atom). These are found at the capped 5'-ends of eukaryotic mRNA.

24. a-
Definition:

A prefix that means "without."

25. A-factor
Definition:

A protein which is found in the bacterial genus Streptomyces that helps start the production of streptomycin and the process of morphological differentiation. It is used in biotechnology to induce these functions in mutant strains of Streptomyces that can't produce it themselves.

26. A-form DNA (A-DNA)
Definition:

One of several forms that can be assumed by a double helix. A-DNA is stable in dehydrated conditions. This form is less common than the dominant form found under physiological conditions -- ß-DNA. This form is also assumed by DNA-RNA hybrid helices and by regions of double-stranded RNA. It is a right-handed helix and is a more compact form than ß-DNA.

27. A-protein (A proteins)
Definition:

A protein found in the cell wall of the bacterium Staphylococcus aureus which binds to the Fc section of immunoglobulins and is therefore used to collect antigen-antibody complexes.

28. aardvark (Orycteropus afer)
Definition:

A nocturnal, burrowing southern African mammal, Orycteropus afer, which is characterized by a long snout and tongue for eating ants and termites. The name "aardvark" is Afrikaans for "earth pig."

29. aardwolf (Proteles cristatus)
Definition:

A carnivorous mammal of South and Eastern Africa (Proteles cristatus) which has grey, black-striped fur, whose diet consists mainly of termites and insect larvae. Aardwolves somewhat resemble hyenas.

30. abasia
Definition:

The inability to walk properly due to paralysis, trembling, or other motor incoordination.

31. abaxial
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

In botany terminology, describes a plant part which is on the side or surface of an organ, facing away from the axis.

32. abdomen
Definition:

1. In higher animals: the portion of the body that contains the intestines and other viscera other than the lungs and heart.
2. In insects and other arthropods: the rearmost segment of the body, which contains part of the digestive tract and all the reproductive organs.

33. abiogenesis
Definition:

The scientific study of how life originally arose on the planet, presumably from nonliving things and the presence of nonliving organic matter.

34. abiogenic
Definition:

Abiogenic refers to things not involved with or produced by living organisms.

35. abioseston
Definition:

Abioseston is a general term for dead organic material floating suspended in ocean water.

36. abiotic
Definition:

"Abiotic" refers to nonliving objects, substances or processes.

37. abiotic stress
Definition:

Nonliving environmental factors (such as drought, extreme cold or heat, high winds) that can have harmful effects on plants.

38. abiotic transformation
Definition:

An abiotic transformation is any process in which a chemical in the environment is altered by non-biological mechanisms (such as by exposure to sunlight).

39. abiotrophy
Definition:

Premature loss of a cell's or tissue's ability to function.

40. ABO blood group (blood type, blood typing)
Definition:

A system of describing the oligosaccharide antigens found on the surface of human blood cells. According to the type of antigen present, a person may be assigned a blood type of A, B, AB or O. A second type of antigen, the Rh factor, renders a "positive" or "negative" blood type. The ABO blood group system is important because it determines who can donate blood to or accept blood from whom. Type A or AB blood will cause an immune reaction in people with type B blood, and type B and AB blood will cause a reaction in people with type A blood. Conversely, type O blood has no A or B antigens, so people with type O blood are "universal donors." And since AB blood already produces both antigens, people who are type AB can accept any of the other blood types without suffering an immune reaction.

The ABO system is also important because it can be used in paternity suits to rule out whether a man is the father of a certain child or not.

41. abomasum
Definition:

The fourth stomach of the cow. The abomasums of suckling calves are used as a source of rennet, a rennin-containing commercial enzyme preparation used to make cheese.

42. abortifacient
Definition:

A drug or compound that induces the expulsion of an embryo or fetus.

43. abortion
Definition:

The expulsion or removal of an embryo or fetus from the mother prematurely; this can be done as an artificial procedure, but it often happens naturally when the mother's body expels the embryo/fetus because it has died, has genetic or developmental defects, or because of infection or illness in the mother. Natural abortions are typically called "miscarriages". Medically-induced abortions, which can be completed with surgery or with hormone drugs, are done because the embryo/fetus is unwanted, deformed, not likely to live, or endangers the mother's life or health.

44. abrin (agglutinin, toxalbumin)
Definition:

A highly poisonous protein found in the seeds of Abrus precatorius, the rosary pea. Abrin is toxic because it inhibits protein synthesis, causing symptoms such as internal bleeding, intestinal upset, and the irritation of mucous membranes. It was formerly used to treat some chronic eye disorders and it is currently being researched as a potential chemotherapy drug.

45. abruptio placentae
Author: Guo Li
Definition:

This is the premature separation of the placenta, i.e. separation of the placenta from the site of implantation on the uterus before the delivery of the fetus. It is a life threatening condition for the fetus and occurs about 1 in 500 to 750 deliveries.

46. abscess
Author: Mirrored from Tsute Chen's Glossary of Microbiology
Definition:

A localized accumulation of pus due to infection.

47. abscisic acid (ABA, abscisin)
Image: View the chemical structure
Definition:

A lipid hormone that inhibits cell growth in plants; it is associated with fruit drop, leaf death and seed dormancy. It is synthesized in the plastids from carotenoids. This hormone helps plants deal with water loss, and its effects can be reversed with gibberellins.

48. abscission
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

The normal shedding from a plant of an organ that is mature or aged, e.g. a ripe fruit, an old leaf. adj. abscissile.

49. absolute filter
Definition:

A fine-pored, steam-sterilizable filter that is used to trap airborne microorganisms. The filter's pores are about 2 micrometers in diameter, smaller than the particles it is designed to remove.

50. absolute gravity
Definition:

In chemistry, the value that denotes the density (specific gravity) at standard conditions (for gases, these conditions are standard atmospheric pressure at 0 C°).

51. absolute risk
Definition:

The excess risk due to exposure to a specific hazard (disease, injury, etc.)

52. absolute zero
Definition:

This is the lowest possible temperature (0 Kelvin, -273.15° Celsius, -459.67° Fahrenheit). At this temperature, all molecular motion stops.

53. absorb
Definition:

To take up liquid or other matter; see absorption.

54. absorbance (optical density)
Definition:

This is a measure of the amount of light absorbed by a suspension of bacterial cells or a solution of an organic molecule; it is measured by a colorimeter or spectrophotometer. Absorbance values are used to plot the growth of bacteria in suspension cultures and to gauge the purity and concentration of molecules (such as proteins) in solution. Absorbance is defined as a logarithmic function of the percent transmission of a wavelength of light through a liquid.

55. absorption
Definition:

The process of absorbing; specifically:

1. In physiology, it refers to the movement of liquids and solutes into cells by way of diffusion or osmosis.
   
2. In chemistry, it refers to the drawing of a gas or liquid into the pores of a permeable solid.
   
3. In immunology, it refers to a process in which an antigen or antibody is used to pull an analogous antigen or antibody out of a solution.
Compare adsorption.

56. absorption spectroscopy
Definition:

This is the use of a spectrophotometer to measure the ability of particles (solutes) in a solution to absorb light through a range of specific wavelengths. Every compound absorbs light differently, so absorption spectra can be used to identify compounds, measure concentrations, and determine reaction rates.

57. absorption spectrum
Definition:

A graph of the amount of light a substance absorbs, plotted as a fuction of energy, frequency or wavelength.

58. abzyme (pl. abzymes)
Definition:

An antibody with catalytic activity.

59. Acanthocephala (spiny-headed worms)
Definition:

A phylum of parasitic organisms, from one of three general classes, generally referred to as spiny-headed worms. They are notable for their lack of a digestive tract. For more information, visit Dr. Peter D. Roopnarine's Acanthocehpala Page.

60. acaulescent
Definition:

Describes a plant that lacks or seems to lack a stem.

61. acceleration phase
Definition:

A period of increasing growth before the log phase in a culture of microbes. After the culture is started on a medium, at first there is no growth (the lag phase), and then the microbes start to gradually grow (acceleration phase) until they reach a constant maximum rate of growth (log phase).

62. acceptable daily intake (ADI)
Definition:

This is an estimate of the amount of a substance in food that can be ingested daily over a lifetime by humans without appreciable health risk. The concept of the ADI has been developed principally by WHO and FAO and is relevant to chemicals such as additives to foods, residues of pesticides and veterinary drugs in foods. ADIs are derived from laboratory toxicity data, and from human experiences of such chemicals when this is available, and incorporate a safety factor. The ADI is thus an estimate of the amount of a substance in food that can be ingested over a lifetime by humans without significant risk to health (for contaminants in food and drinking water, tolerable intakes - daily or weekly - are used). See tolerable daily intake.

63. acceptable risk
Definition:

This relates to the potential for suffering disease or injury that will be tolerated by an individual, group, or society in exchange for the benefits of using a substance or process that will cause such disease or injury. Acceptability of risk depends on scientific data, social, economic, and political factors, and on the perceived benefits arising from a chemical or process that creates the risk(s) in question.

64. acceptor control
Definition:

The regulation of the respiration rate, governed by ADP's ability to be a phosphate group acceptor.

65. accessory flower parts
Author: Mirrored from Dave Sutton's Aquatic Plant Glossary
Definition:

Sepal and petal organs found on flowers. The sepals and petals are not essential for pollination but may aid in attracting insects or other organisms.

66. accessory fruit
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

A fruit, or group of fruits derived from one flower, in which the conspicuous, fleshy portion develops from the receptacle and is shed with the true fruit(s) attached.

67. accessory pigments
Definition:

Light-absorbing pigments such as carotenoids and phycobilins that serve as complements to chlorophyll in plants, algae and bacteria by trapping light energy for photosynthesis.

68. acclimatization (adaptation)
Definition:

The physiological process through which an organism grows accustomed to a new environment. In microbial cultures, this can involve enzymatic changes that allow it to use an new nutrient source for energy.

69. accrescent
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

Increasing in size with age, as the calyx of some plants after flowering.

70. accretion
Definition:

A gradual growth through accumulation of more units. For example, the collection of cells on a filter would be an accretion of the cells.

71. accumbent
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

In botany terminology, describes the orientation of an embryo, with the radicle lying against the edges of the two cotyledons.

72. accumulation
Definition:

Repeated exposures to a chemical may result in the progressive increase of its concentration in an organism, organ or tissue; illness or other effects may increase with successive doses. Factors involved in accumulation include selective binding of the chemical to tissue molecules, concentration of fat soluble chemicals in body fat, absent or slow metabolism of the chemical, and slow excretion of the chemical. Accumulation is a mass balance effect where input exceeds output.

73. ACE Inhibitor (ACE inhibitor)
Author: PharmInfoNet
Definition:

A type of drug used to lower blood pressure. Studies indicate that it may also help prevent or slow the progression of kidney disease in people with diabetes.

74. acellular
Definition:

Describes any organism or tissue that is a mass of protoplasm which is not divided into cells, such as the plasmodium of some slime molds and the hyphae of some fungi.

75. acellular vaccine
Author: Mirrored from Tsute Chen's Glossary of Microbiology
Definition:

Vaccine consisting of antigenic parts of cells.

76. acentric
Definition:

This term refers to a chromosome or chromatid that lacks a centromere; this condition can result during crossing over in which the normal, centromere-containing segment is replaced by an inverted segment that lacks a centromere.

77. acervulus
Definition:

A flat, often round mass of hyphae which carry spore-bearing parts called conidophores; acervuli are found in fungi belonging to the order Melanconiales.

78. acesulfames
Image: View the chemical structure
Definition:

A class of artificial sweeteners derived from oxathiazinone; some varieties are over a hundred times sweeter than table sugar (sucrose).

79. acetabulum
Definition:

A cuplike socket in the pelvis into which the head of the thigh bone (femur) fits. Also, in entomology, the leg socket on an insect's abdomen or thorax.

80. acetaminophen (Tylenol, Panadol, acetylaminophenol)
Definition:

This white, somewhat-water-soluble chemical is most widely known as an over-the-counter painkiller (analgesic) and fever reducer, but it is also used to make azo dyes and photographic chemicals. Acetaminophen melts at 168 C°. and can cause liver damage in high overdoses.

81. acetarsone
Definition:

An arsenic-containing compound administered to treat infections of the parasite protozoan Entameba histolytica in the intestine or genitourinary tract.

82. acetate
Definition:

A salt or ester of acetic acid; specifically, a synthetic textile fiber made from partially hydrolyzed cellulose acetate, or a plastic-like film made from cellulose triacetate.

83. acetic acid (ethanoic acid)
Image: View the chemical structure
Definition:

The acid most commonly associated with vinegar; it is the most commercially important organic acid and is used to manufacture a wide range of chemical products, such as plastics and insecticides. It is produced naturally by Acetobacter but, except for making vinegar, is usually made through synthetic processes.

84. acetic fermentation
Definition:

A type of fermentation conducted by certain microbes in which organic materials are broken down into acetic acid to generate ATP for energy.

85. acetin (monoacetin)
Definition:

A thick, colorless, water-attracting liquid which is used as a food additive and dye solvent and in explosives manufacture and leather tanning. It is created by heating and then distilling a mixture of acetic acid and glycerol.

86. Acetobacter
Definition:

Acetobacter is a genus of rod-shaped, flagellated or nonmotile Gram-negative bacteria that oxidize ethanol to acetic acid. These bacteria are commonly found on fruits and vegetables, and although they are used commercially to produce vinegar (especially Acetobacter aceti), they're considered pests by brewers and vintners.

87. acetoclastic bacteria
Definition:

Bacteria that use only acetic acid and produce methane during anaerobic fermentation.

88. acetoclastis
Author: Mirrored from Tsute Chen's Glossary of Microbiology
Definition:

The process of splitting acetate into methane and carbon dioxide by some methanogens.

89. acetogenic bacteria
Definition:

Bacteria that convert carbon dioxide to acetic acid or turn sugars into acetate.

90. acetohexamide (Dymelor)
Author: PharmInfoNet
Definition:

A pill taken to lower the level of glucose in the blood. Only some people with noninsulin-dependent diabetes take these pills.

91. acetone (2-propanone)
Definition:

A colorless, flammable liquid which is used as a solvent (it is most familiar as the solvent in nail polish remover). The simplest ketone, it mixes with water, ethyl alcohol, and most oils. It melts at -95.4 C°. and boils at 56.2 C°. It is naturally found in very tiny quantities in the body fluids and tissues of healthy people and in somewhat larger amounts in people suffering from diabetes or starvation.

92. acetone-butanol fermentation
Definition:

The formation of acetone and butanol through the anaerobic fermentation of glucose by Clostridium acetobutylicum. However, most industrial plants make acetone and butanol through synthetic processes that use petrochemicals.

93. acetyl
Definition:

CH₃CO- This is the radical of acetic acid; it contains a carbonyl and a methyl group.

94. acetyl coA synthase
Definition:

This enzyme is found in bacteria and plants; it catalyzes the reaction in which acetate enters metabolic pathways and forms acetyl coenzyme A.

95. acetyl coenzyme A (acetyl CoA)
Definition:

This coenzyme plays a huge role in intermediary metabolism, in which cells synthesize, break down or use nutrient molecules for energy production, growth, etc.

96. acetyl group
Definition:

A CH₃CO- group on a larger molecule, where the -CH₃ (a methyl group) is single-bonded to the carbon, an oxygen is single-bonded to the carbon, and the carbon has two other bonds to the rest of the molecule.

97. acetyl reduction assay (acetylene reduction assay)
Definition:

A technique for measuring the nitrogen fixation activity in photosynthetic organisms. It uses a flame ionization detector and a gas chromatography apparatus to determine the reduction of acetylene to ethylene by the enzyme nitrogenase.

98. acetyl-CoA pathway
Author: Mirrored from Tsute Chen's Glossary of Microbiology
Definition:

A pathway of autotrophic carbon dioxide fixation commonly happened in obligate anaerobes such as methanogens, homoacetogens, and sulfate reducing bacteria.

99. acetylcholine
Definition:

A chemical found in vertebrate neurons that carries information across the synaptic cleft, the space between two nerve cells.

100. acetylcholinesterase
Definition:

An enzyme that breaks down unused acetylcholine in the synaptic cleft (the space between neurons); this enzyme is necessary to restore the synaptic cleft so it is ready to transmit the next nerve impulse.

101. acetylsalicylic acid (aspirin)
Image: View the chemical structure
Definition:

An odorless, white, slightly bitter drug used to reduce pain, fever, inflammation and sometimes to prevent blood clotting. Some people cannot tolerate it because it can cause stomach bleeding, however. It is soluble in both water and alcohol and melts at 132 - 136 C°.

102. acetylserotonin
Definition:

An acetylated (has a CH₃CO- group attached) form of the hormone serotonin. Along with serotonin and the hormone melatonin, it is produced in the pineal gland in the brain.

103. achalasia
Author: Guo Li
Definition:

This is a disorder of esophageal peristalsis characterized by degeneration of the ganglion cells of the lower esophagus. This results in the failure of the relaxation of the cardiac sphincter during the passage of food. There is a potential of developing carcinoma of the esophagus in 5 to 10 % of such patients.

104. achalasia of the cardia
Definition:

A medical term describing the inability to relax the sphincter muscle separating the esophagus and stomach while swallowing.

105. achiasmatic
Definition:

Undergoing meiosis, a process where the cell's nucleus divides, without reaching the stage at which homologous chromatids pair to exchange genetic material (called chiasmata).

106. achiral
Definition:

A term used to describe a molecule which, in a given configuration, is superimposible on its mirror image. This is in contrast to chiral molecules which cannot be superimposed on their mirror images.

107. acholia (acholic)
Definition:

Absence of or failure to secrete bile.

108. acholuria
Definition:

Medical term describing the absence of bile pigment in the urine; usually in the context of describing a type of jaundice characterized by this.

109. acicular
Definition:

Resembling a needle (typically used to describe the leaf of a plant).

110. acicular
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

In botany terminology, describes a plant part which is needle-shaped and stiff.

111. aciculate
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

In botany terminology, describes a plant part which is finely scored on the surface, as if scratched by a pin.

112. acid (adj. acidic) (Arrhenius acid, Lewis acid, Bronsted acid)
Definition:

A fundamental category of many compounds whose water-based solutions have a sour taste, turn blue litmus paper red, and can combine with metals to form salts. Acids have a pH lower than 7 (strong acids have a pH of less than 3). Specific types of acids include:
1. Arrhenius acid: any chemical that increases the number of free hydrogen ions (H⁺) when they're added to a water-based solution. The more free hydrogens produced, the stronger the acid.
2. Brönsted or Brönsted-Lowry acid: any chemical that acts as a proton donor in a chemical reaction.
3. Lewis acid: any chemical that accepts two electrons to form a covalent bond during a chemical reaction.

113. acid dissociation constant (acid ionization constant)
Definition:

This is the equilibrium constant for the breaking apart of a weak acid into its hydrogen and conjugate base in a water solution.

114. acid mine drainage
Author: Mirrored from Tsute Chen's Glossary of Microbiology
Definition:

The process to draw off acidic water from a natural mine rich in sulfide minerals which have been oxidized to sulfuric acid by microbial actions.

115. acid phosphatase
Author: Guo Li
Definition:

This is an enzyme produced by cells in the prostate (a gland that surrounds the urethra in the base of the penis). It is used to diagnose and follow the progression of prostate cancer. Its level is elevated in prostate cancer, multiple myeloma, bony metastasis of cancers, and is falsely elevated after prostate surgery or examination.

Normal range: range 0.11-0.6 IU/L

116. acid proteases
Definition:

Any of many protein-hydrolyzing enzymes that work best in an acidic solution (usually in a pH range of 2-6). Such proteases include the stomach enzymes pepsin and rennin. Similar proteases produced by fungi such as Aspergillus oryzae are used in the manufacture of flour and soy sauce.

117. acid rain
Definition:

This is rain which has turned acidic because of the presence of sulfur or nitrogen oxides (both created from burning coal and other fossil fuels) in the atmosphere. Acid rain is a serious environmental problem; it can kill trees and harm plants and animals in lakes and ponds.

118. acid-fast stain
Author: Mirrored from Tsute Chen's Glossary of Microbiology
Definition:

A staining technique used to determine the cell wall property of a microorganism. After stained with dye such as hot carbolfuschin, an acid-fast organism, (.e.g. Mycobacterium species) will retain the color in its cell wall after being washed with acid-alcohol.

119. acidogenic fermentation
Definition:

Any fermentation that produces a weak acid, such as lactic acid.

120. acidophile
Definition:

Describes any microorganism that can or must live in an acidic environment (pH below 6).

121. acidosis
Definition:

A metabolic illness that occurs when the body's ability to buffer free hydrogen ions in the blood is compromised, which usually causes the pH of the blood to drop (the blood gets more acidic). Compare alkalosis.

122. acidulants
Definition:

Food additives that are used to impart a sharp flavor. The most common acidulant is citric acid (produced by the fermentation of molasses or other sugars by the fungus Aspergillus niger). Malic acid and fumaric acid are also frequently used.

123. acne
Author: Guo Li
Definition:

This is a skin disease of the face, back and shoulders. It involves overactive sebaceous glands with plugged hair follicles inside which there is growth of an acne bacteria.

124. acoelomate
Definition:

A triploblastic organism which does not have an internal body cavity other than the gut. The area between the gut and the organism's outer body wall is completely filled with tissue derived from the mesoderm. The term is used to classify multicellular animals by developmental pattern.

125. acoustic neuroma
Author: Guo Li
Definition:

This is a tumor of Schwann cells in the cerebellopontine angle.

126. acre-foot-of-water
Author:
Definition:

The amount of water needed to cover one acre to a depth of one foot. It consists of 326,000 gallons of water.

127. acridine orange
Image: View the chemical structure
Definition:

3,6-bis(dimethylamino)acridinium chloride. A toxic, fluorescing dye that stains DNA and RNA and is typically used to identify cancerous tumor cells. When it binds to double-stranded DNA, it fluoresces green; when it binds with the phosphate groups of single-stranded DNA or RNA, it fluoresces orange. The chemical also causes frameshift mutations.

128. acroblast
Definition:

A granule within the young sperm cell (a spermatid) that eventually becomes the acrosome or caplike frontal portion of the mature sperm cell.

129. acrocentric
Definition:

A chromosome or chromatids with a non-centrally-located centromere, producing chromosome arms with unequal lengths.

130. acrocentric
Definition:

An acrocentric chromosome has its centromere closer to one end than to the other, resulting in unequal chromosome arms.

131. acromegaly
Author: Guo Li
Definition:

Acromegaly is a hormonal disorder in which there is excessive secretion of the growth hormone resulting in enlargement of hands, feet, face, tongue, jaws and internal organs. The cause is usually a benign pituitary adenoma.

132. acropetal
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

In botany terminology, describes a plant part which is arising or developing in a longitudinal sequence beginning at the base and proceeding towards the apex.

133. acrosin
Definition:

An enzyme found in sperm cells which is thought to help the sperm penetrate the tough outer surface of the ovum.

134. acrosome
Definition:

A membrane-bound section at the tip of the head of a sperm which contains lytic enzymes (hyaluronidase in mammalian sperm) which break down the outer coat of the egg and allow the sperm to inject its haploid DNA.

135. acrosome
Definition:

Anterior membrane-bound compartment covering the sperm head that contains lytic enzymes, which help the sperm digest through the tough outer surface of the egg. The compartment is secreted by the Golgi apparatus of the spermatid (young sperm cell).

136. acrosome reaction
Author: Fertilitext
Definition:

A chemical change that enables a sperm to penetrate an egg.

137. acrostichoid
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

Of sporangia, densely covering the abaxial surface of the fertile frond, i.e. not in distinct groups; of ferns, having the sporangia arranged as above.

138. acrosyndesis
Definition:

A type of pairing that occurs during meiosis, a process where the cell's nucleus divides, which involves the terminal portions of homologous chromosomes.

139. acrylonitrile
Definition:

A colorless liquid which will mix somewhat with water, mixes well with all common organic solvents, and is toxic, carcinogenic (cancer-causing), and a fire hazard. Freezing point: -83 C°. Boiling point: 77.5-77.9 C°. It is used as a monomer for acrylic fibers and acrylic rubber and other industrial purposes.

140. actin
Definition:

One of two proteins involved in muscle contraction (see also myosin). Actin is found in both smooth and striated muscle and also serves as an important structural molecule for the cytoskeletons of many eukaryotic cells.

141. actinide (actinoid)
Definition:

Any element in the periodic table which has an atomic number between 89 and 103.

142. actinomorphic
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

Of flowers: symmetrical about more than one vertical plane.

143. Actinomycetes
Author: Mirrored from Tsute Chen's Glossary of Microbiology
Definition:

Gram-positive bacteria that can form branching filaments. They may form true mycelia or produce conidiospores.

144. actinomycin D
Definition:

A relatively toxic antibiotic produced by the funguslike bacterium Streptomyces parvallum. It inhibits RNA transcription in eukaryotes and has antitumor properties, so it is often used in conjunction with other drugs in chemotherapy.

145. action potential (nerve impulse)
Definition:

The sequential, electrochemical polarization and depolarization that travels across the membrane of a nerve cell (neuron) in response to stimulation (touch, pain, cold, etc.)

146. activated carbon (activated charcoal)
Definition:

A type of carbon produced through exposing a source material such as wood or bone to very high temperatures in the presence of steam, air, or carbon monoxide. Activated carbon is very good at removing (adsorbing) contaminants and is used in water filters, to decolor solutions, and is sometimes administered to poisoning victims.

147. activated sludge process
Definition:

A method of treating sewage and wastewater through microbial oxidation. Sewage previously treated in settling tanks is aerated to encourage the growth of nonpathogenic aerobic microorganisms (bacteria, yeasts, molds and protozoans) which break the organic matter down into carbon dioxide, water, and simple salts. After this activated sludge is produced, the wastewater undergoes further processing through anaerobic digestion, filtering, and chlorination.

148. activation energy ( G, delta G)
Definition:

The amount of energy (expressed in joules) that is needed to convert all the molecules in one mole of a reacting substance from a ground state to the transition state.

149. activator
Definition:

In biochemistry:
1. A DNA-binding protein that regulates one or more genes by increasing the rate of transcription.
2. A metabolite that positively modulates an allosteric enzyme.

150. active biomass
Definition:

The amount of a given culture that is actively growing.

151. active immunity (active immunization)
Definition:

An organism's resistance to disease or infection, developed because the organism's immune system has produced antibodies after an infection or innoculation.

152. active metal
Definition:

Any very reactive metal, such as magnesium or sodium; most are located in the first two columns of the periodic table.

153. active site (binding site)
Definition:

A specific region of an enzyme where a substrate binds and catalysis takes place.

154. active transport
Definition:

Transport of ions, nutrients or other molecules into a cell against a concentration gradient; this requires the expenditure of energy through ATP hydrolysis.

155. activity
Definition:

The potential or true thermodynamic activity of a substance, as opposed to its molar concentration.

156. activity coefficient
Definition:

The factor by which the value of a concentration of a solute must be multiplied to determine its true thermodynamic activity.

157. aculeus (pl. aculei)
Author: Mirrored from Dave Sutton's Aquatic Plant Glossary
Definition:

A prickle growing from bark.

158. acumen
Author: Mirrored from Dave Sutton's Aquatic Plant Glossary
Definition:

The point of an acuminate leaf.

159. acuminate
Definition:

Descibes a leaf that tapers abruptly to a sharp point.

160. acuminate
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

Tapering gradually to a protracted point.

161. acuminate
Author: Mirrored from Dave Sutton's Aquatic Plant Glossary
Definition:

Drawn out into a long point; tapering point.

162. acute
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

Terminating in a distinct but not protracted point, the converging edges separated by an angle less than 90°.

163. acute
Author: Mirrored from Tsute Chen's Glossary of Microbiology
Definition:

Used to describe a short-term infection or disease which is characterized by dramatic onset and rapid recovery.

164. acute toxicity
Definition:

Illness resulting from a single dose or exposure to a toxic substance. Compare chronic toxicity.

165. acute toxicity
Author: Biological Sciences at Heriot-Watt University
Definition:

Adverse effects occurring within a short time of administration of a single dose of a chemical, or immediately following short or continuous exposure, or multiple doses over 24 hours or less.

166. acute tubular necrosis (ATN)
Author: Guo Li
Definition:

This is renal failure characterized by sudden drop in urinary output and the steady increase of serum urea nitrogen and creatinine levels. Common causes of ATN are hypotension, sepsis, burns, and eclampsia. The urine specific gravity is 1.010 or less (loss of ability to concentrate). In the recovery phase, high output failure (low specific gravity, large volume, and lack of ability to excrete nitrogen or potassium) is often the case.

167. acycloguanosine (acyclovir)
Image: View the chemical structure
Definition:

An antiviral medication used to treat herpesvirus infections; it works by inhibiting viral DNA synthesis.

168. acyl carrier protein (ACP)
Definition:

A small (77 peptides long) protein which binds six other enzymes involved in fatty acid synthesis. It was first isolated in E. coli bacteria.

169. ad
Definition:

This Latin term, which is frequently used in medicine, means "to" or "up to".

170. ad libitum (ad lib.)
Definition:

This Latin term, which is frequently used in medicine, means "at pleasure".

171. Adams-Stokes syndrome (Stokes-Adams syndrome)
Author: Guo Li
Definition:

Adams-Stokes syndrome is the recurrent episodes of near loss or loss of consciousness associated with transient or permanent problems in the conduction of electrical activity between the atrium and the ventricles of the heart.

172. adaptation
Author:
Definition:

The condition of showing fitness for a particular environment, as applied to characteristics of a structure, function or entire organism; a modification of a species that makes it more fit for reproduction and/or existence under the conditions of its environment.

173. adaptive radiation
Definition:

The evolution of new species or sub-species to fill unoccupied ecological niches.

174. adaptors
Definition:

Short synthetic oligonucleotide strands that have one sticky end and one blunt end; the blunt ends join to the blunt end of a DNA fragment, forming a new fragment with two sticky ends that can be more easily spliced into a vector.

175. adaxial
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

Facing towards the axis. Compare abaxial.

176. addiction (substance abuse)
Author: Guo Li
Definition:

This is the state of being physically or psychologically dependent on some substance. Common abused substances include:
• ethyl alcohol (grain alcohol)
• opioids (opium, heroin, hydrocodone, hydromorphone, oxycodone, meperidine [Demerol])
• hallucinogens (LSD, psilocybin, DMT, morning glory seeds)
• mescaline, MDA, PMA, STP
• amphetamines
• cocaine
• inhalants (solvents and aerosols)

177. Addison's disease
Author: Mirrored from Guo Li's Dictionary of On-Line Medical Resources
Definition:

This is a disease of the adrenal gland. The usual symptoms are weakness, easily feeling tired, loss of appetite, and sparse hair growth in some areas. Cortisol levels in the blood is low or absent.

178. addition polymer
Definition:

A polymer which is formed from the fusion of two monomers which join completely without losing any small molecules.

179. additive effect
Definition:

An additive effect is the overall biological effect two chemicals acting together and which is the simple sum of the effects of the chemicals acting independently. Compare antagonism.

180. additive genetic variance
Author: ForBio Ltd.
Definition:

The proportion of genetic variation that is the summation of the effect of all individual genes influencing a trait.

181. adduct
Definition:

1. A compound produced by the mixing of two or more chemicals.
2. A complex that forms when a chemical binds to a biological molecule, such as DNA or protein.

182. adduct
Definition:

A compound formed by the fusion of two molecules (or, less often, atoms) which are then held together by a coordinate covalent bond.

183. adenine
Image: View the chemical structure
Definition:

A nitrogenous base, one member of the base pair A- T (adenine-thymine).

184. adenocarcinoma
Definition:

A cancerous tumor originating in glandular tissue.

185. adenoids
Definition:

A mass of lymphatic tissue at the back of the throat and behind the nose. "The adenoids" is a popular term for the swelling or enlargement of this tissue, which sometimes occurs in children and which makes breathing difficult.

186. adenoma
Definition:

A benign tumor that develops from glandular tissue.

187. adenosine
Definition:

A ribonucleoside which consists of the nitrogenous base adenine linked to the sugar ribose.

188. adenosine deaminase deficiency (ADA)
Definition:

Inherited disorder caused by insufficient adenosine deaminase activity, resulting in a compromised immune system.

189. adenosine diphosphate (ADP)
Image: View the chemical structure
Definition:

ADP is a molecule which consists of the nitrogenous base adenine linked to the sugar ribose and which has a chain of two phosphate groups attached to the ribose in a linear fashion. ADP is used as an intermediate throughoug glycolysis. ATP hydrolyzes to produce ADP and free energy.

190. adenosine triphosphate (ATP)
Image: View the chemical structure
Definition:

ATP is a molecule which consists of the nitrogenous base adenine linked to the sugar ribose and which has a chain of three phosphate groups attached to the ribose in a linear fashion. ATP is present in all living cells and serves as an energy source for many metabolic processes; energy is released when ATP is hydrolyzed into ADP. ATP is required for ribonucleic acid synthesis since it is a direct precursor. It is the single most important molecule in all living things since it serves as the currency for energy in biological systems.

191. adenovirus
Definition:

An icosahedral (20-sided) virus that contains DNA (as opposed to RNA); there are over 40 different adenovirus varieties, some of which cause the common cold.

192. adenylate cyclase
Definition:

This is an enzyme responsible for the catalysis of cAMP from ATP.

193. adherence
Author: Mirrored from Tsute Chen's Glossary of Microbiology
Definition:

Refers to the ability of bacteria adhere (stick) to host surfaces.

194. adhering junction (desmosome)
Definition:

A type of junction between cells forming tissues that are subjected to stretching and pulling, such as the skin. This type of junction provides very tight contact between adjacent cells and allows the cells to fuction as a unit. Belt desmosomes are attachment sites that circle the cell, and spot desmosomes are small points of attachment across the cell's surface.

195. adipocyte (fat cell)
Definition:

An animal cell that stores fat.

196. adipose tissue
Definition:

Connective tissue that has been specialized to store fat.

197. adjacent wetlands
Author:
Definition:

The term adjacent means bordering, continguous, or neighboring. Wetlands separated from other waters of the United States by man-made dikes or barriers, natural river berms, beach dunes, and the like are adjacent wetlands.

198. adjuvant
Definition:

1. In pharmacology, a substance that, when added to a medicine, speeds or improves its action.
2. In immunology, a substance that is added to a vaccine to improve the immune response so that less vaccine is needed to produce more antibodies. Such adjuvants apparently work by speeding the division of lymphocytes and by keeping the antigen in the area where the immune response is taking place. In research with humans, aluminum phosphate and aluminum hydroxide gel are commonly used; in research involving lab animals, Freund's adjuvant is used.

199. adjuvant therapy
Definition:

Cancer treatment that involves surgery followed by additional treatment with chemotherapy drugs and/or radiation to reduce the risk that the cancer will return.

200. adnate
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

In botany terminology, describes a plant part which is fused to an organ of a different kind, e.g. a stamen fused to a petal.

201. adoptive immunity
Definition:

Immunity to disease or infection conferred on a previously non-immune individual by transferring lymphocytes from a previously immune individual to the non-immune individual.

202. adoral
Definition:

An adoral location indicates proximity to an organism's mouth. The adoral side of an organism is the side where the mouth is located.

203. adrenal cortex
Definition:

This is the outer portion of the adrenal gland; it secretes hormones such as hydrocortisone (a glucocortoid) and aldosterone (a mineralocorticoid). Glucocortoids help cells synthesize glucose, catabolize proteins, mobilize free fatty acids, and inhibit inflammation in allergic responses. Mineralocortoids regulate the levels of minerals such as sodium and potassium in the blood.

204. adrenal gland
Definition:

This gland is found above each kidney, and it made up of an outer wall (cortex) that secretes important steroid hormones and an inner portion (medulla) that produces adrenaline (epinephrine) and noradrenaline (norepinephrine).

205. adrenergic
Definition:

Refers to neurons that use catecholamines (adrenaline, dopamine and noradrenaline) as neurotransmitters.

206. adrenocorticotrophic hormone (ACTH)
Definition:

A peptide hormone produced by the anterior pituitary gland. It stimulates the adrenal cortex to secrete glucocorticoid hormones, which help cells synthesize glucose, catabolize proteins, mobilize free fatty acids, and inhibit inflammation in allergic responses.

207. adrenogenital syndrome
Author: Guo Li
Definition:

Adrenogenital syndrome is the autosomal recessive form of congenital adrenal hyperplasia due to 21-hydroxylase deficiency. 21-hydroxylase is an enzyme needed in the synthesis of cortisol. Diminished levels of cortisol results in excessive secretion of ACTH which stimulates adrenal hyperplasia which secretes excessive androgen. Affected genetic females under the influence of androgen would display masculine characteristics such as hirsutism (excessive body hair), small breasts, heavy arms and legs and enlarged clitoris. Affected genetic males display enlargement of penis with small testes, and increased pigmentation. With early treatment, prognosis is good.

208. adriamycin (doxorubicin injection)
Definition:

An antibiotic manufactured by Pharmacia which is used to treat certain types of cancer (such as breast carcinomas). It is also a cardiotoxin and can cause heart failure at high cumulative dosages (above a total dose of 300 mg/m²).

209. adsorb
Definition:

Refers to the process of one material attracting and holding molecules of another substance to the surface of its molecules.

210. adsorption
Definition:

1. In chemistry, refers to the accumulation of molecules of a gas or liquid on the surface of another substance; note that the accumulating molecules do not actually penetrate the substance they're on.
   
2. In virology, refers to the adhesion of a substance to an organic particle in a solution, e.g. the adhesion of a virus to a cell.
Compare absorption.

211. adsorption fermentation (extractive fermentation)
Definition:

A fermentation technique in which products of the fermentation are removed from the broth by adsorption onto materials such as carbon or polymers. Generally, the preferred method of doing this is to circulate the fermenting broth through the adsorbent substrate, because the fermentation products are often toxic to the microbes.

212. adult respiratory distress syndrome (ARDS)
Author: Guo Li
Definition:

Adult respiratory distress syndrome is a clinical condition in which there is shortness of breath, abnormal findings in chest x-ray, and low oxygen levels in the blood. It is usually associated with injury to the lung, and preceded with a variety of factors; including trauma, infection, pancreatitis, shock, burns, among many others.

213. adventitious
Definition:

Describes roots or shoots or other parts that grow in an uncharacteristic place on a plant (such as roots growing from leaves).

214. adventive
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

In botany terminology, describes a plant which has been introduced to an area recently, in particular since colonization by humans.

215. adverse effect
Definition:

This is an abnormal or harmful effect to an organism caused by exposure to a chemical. It is indicated by some result such as death, a change in food or water consumption, altered body and organ weights, altered enzyme levels, or visible illness. An effect may be classed as adverse if it causes functional or anatomical damage, causes irreversible change in the homeostasis of the organism, or increases the susceptibility of the organism to other chemical or biological stress. A non-adverse effect will usually be reversed when the organism is no longer being exposed to the chemical.

216. aerenchyma
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

In plants, tissue incorporating large, gas-filled spaces interspersed with the cells in a characteristic pattern.

217. aerenchymous tissue (aerenchyma)
Author:
Definition:

A type of plant tissue in which cells are unusually large, resulting in large air spaces in the plant organ; such tissues are often referred to as spongy and usually provide increased buoyancy.

218. aerial
Definition:

Something that is found in or takes place in the air.

219. aerie
Author:
Definition:

A protected location on a cliff used by predatory birds as a site for rearing their young.

220. aerobe
Definition:

An organism that can or must live in an oxygen-containing environment and which uses oxygen as the terminal electron acceptor in respiration.

221. aerobic
Definition:

In the presence of, or requiring, oxygen.

222. aerogenic
Author: Mirrored from Tsute Chen's Glossary of Microbiology
Definition:

Gas-producing, e.g., aerogenic fermentation.

223. aerosol
Definition:

A suspension or dispersion of fine particles of a solid or liquid in a gas.

224. aerospace medicine
Definition:

A field of medicine which specializes in the effects of atmospheric and space flight on human physical and psychological well-being.

225. aerotaxis
Definition:

An organism's movement toward or away from oxygen as a reaction to its presence. The term is most often used when discussing aerobes (oxygen-using) versus anaerobes (which don't use oxygen).

226. aerotolerant
Definition:

Able to survive in the presence of oxygen. This term especially applies to facultative anaerobes, which don't actually require oxygen to live but are not harmed by its presence.

227. aerotropism
Definition:

An organism's growth or movement in the direction of oxygen. In botany: a plant root's growth away from the natural direction due to the action of oxygen or other gases.

228. AFC (antibody-forming cells)
Definition:

Stands for "antibody-forming cells," which are B cells (plasma cells) that are dedicated to producing secreted antibodies.

229. afferent
Definition:

Moving or carrying inward or toward a central part. Refers to vessels, nerves, etc. For example, blood vessels carrying blood toward the heart, or nerves conducting signals to the brain. Compare efferent.

230. affinity
Definition:

Attraction between particles or substances to other particles or substances. In biological and biochemical fields, this term generally is a measure of the attraction of one biological molecule toward another molecule (which can be organic or inorganic), either to alter it, destroy it, or form a compound with it. Examples are enzymes and their substrates, or antibodies and their antigens.

231. affinity adsorbent
Definition:

A support matrix coated with an affinity ligand that is able to selectively absorb substances such as enzymes, proteins, and antibodies.

232. affinity chromatography
Definition:

A technique of analytical chemistry used to separate and purify a biological molecule from a mixture, based on the attraction of the molecule of interest to a particular ligand which has been previously attached to a solid, inert substance. The mixture is passed through a column containing the ligand attached to the stationary substance, so that the molecule of interest stays within the column while the rest of the mixture continues through to the end. Then, a different chemical is flushed through the column to detach the molecule from the ligand and bring it out separately from the rest of the mixture.

233. affinity labeling
Definition:

A method for tagging molecules, such as enzymes, so that they can be more easily detected and studied. The method works by substituting a synthetic substance which is similar to the substance that the enzyme normally bonds with.

234. afibrinogenemia (adj.: afibrinogenemic)
Definition:

A rare blood disease where the blood has difficulty clotting due to the lack of fibrinogen, or clotting factor I, in the blood.

235. aflatoxin
Image: View the chemical structure
Definition:

A fungal toxin which is a powerful liver carcinogen. It is produced by Aspergillus flavus and A. parasiticus, which grow easily on beans, grains, and peanuts which are inappropriately stored in warm, humid conditions. The presence of aflatoxins in contaminated food supplies is thought to contribute to the high levels of liver cancer in undeveloped and developing countries.

236. African green monkey kidney cells
Definition:

Cells taken from the kidneys of the African green monkey Cercopithecus aethiops sabaeus and used to grow certain viruses like poliovirus.

237. African rock python (Python sebae)
Definition:

The largest of African snakes, Python sebae can reach over twenty feet in length. It stays mostly near water and has a range from the Sahara desert to South Africa. For more information, visitthe Portland Zoo's Python Page.

238. African sleeping sickness
Definition:

A disease affecting humans and other mammals in central Africa that is caused by the parasitic protozoans Trypanosoma brucei gambiense and Trypanosoma brucei rhodesiense and is transmitted by the tsetse fly. Symptoms include fever, chills, headache, vomiting, pain in the extremities, lymph gland enlargement, anemia, depression, fatigue, coma, and eventually death if left untreated. The trypanosome is able to evade the host's immune system by frequently changing the proteins on its outer surface, by which the immune system identifies intruders.

239. agameon
Definition:

An organism that reproduces asexually only, without producing gametes (sperm or eggs).

240. agammaglobulinemia (adj.: agammaglobulinemic)
Definition:

A rare disease where the body is unable to produce immune antibodies due to the lack of gamma globulin, a type of immunoglobulin, in the blood. The disease can be acquired or inherited as an X-linked recessive genetic disease.

241. agar
Definition:

This gelatinous material, an extract from red algae (mainly Gelidium and Gracilaria species), is most frequently used as a culture medium, especially for bacteria. It is also used as a thickener in foods, but humans can't digest it.

242. agar-gel reaction
Definition:

The reaction between an antibody and an antigen during an immunology lab procedure where the two are allowed to diffuse toward each other through an agar-gel medium. Lines of precipitation form in the places on the gel where the two react with each other and shows where the reaction has occurred.

243. agarose (agarbiose)
Definition:

This linear galactan is created by purifying agar; when it is heated and cooled, it forms a gel that is used as a support for many types of electrophoresis and immunodiffusion. A typical gel is about 1% agarose. Agarose is more porous than acrylamide and is sold in different grades; the lower its sulfate content, the more highly purified it is.

244. agarose gel electrophoresis
Definition:

A type of electrophoresis that uses a matrix of highly purified agar to separate large DNA and RNA molecules (generally around 20,000 nucleotides in size).

245. age-class
Author:
Definition:

A group of individuals of a species that have the same age.

246. agenesis
Definition:

A condition in which a part of the body (such as an organ or a tissue) doesn't completely develop or fails to develop at all.

247. agglutination
Definition:

1. The clumping together of cells due to the binding of agglutinin (a protein) molecules on each cell's surface.
   
2. The clumping together of two organisms of the same species for the purpose of sexual reproduction. Often conducted by means of a carbohydrate on one organism and a protein on the other, resulting in a glycoprotein.

248. aggradation
Author:
Definition:

The geologic process by which stream beds, floodplains, and the bottoms of other water bodies are raised in elevation by the deposition of material eroded and transported from other areas (opposite of degradation).

249. aggrading stream
Author:
Definition:

A stream which is depositing more material than it is removing (or eroding). It is said to be depositional.

250. aggregate fruit
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

A cluster of fruits formed from the free carpels of one flower. Compare syncarp.

251. aggressin
Definition:

A term for a protein produced by a pathogenic microbe which aids its spread in the host by inhibiting the host's immune system (specifically the response by phagocytes).

252. aging, ageing
Definition:

1. The physiological processes that occur in an organism as it gets older.
2. A medical discipline that deals with the study of the biological/physiological processes that affect human adults as they get older.

253. agitator (impeller)
Definition:

This device is used to stir or shake up a mixture; the types generally used are flat blade, marine screw, turbine, and variable pitch screw.

254. aglycon (aglucone)
Definition:

This is the non-carbohydrate part of a glycoside.

255. agnosia
Author: Mirrored from Guo Li's Dictionary of On-Line Medical Resources
Definition:

The loss of the ability to recognize objects, people, sounds, shapes, or smells.

256. agonist
Definition:

Any molecule that improves the activity of a different molecule; e.g., a hormone, which acts as an agonist when it binds to its receptor, thus triggering a biochemical response.

257. agonist
Author: PharmInfoNet
Definition:

A drug that both binds to receptors and has an intrinsic effect.

258. agonistic animal behavior
Definition:

Aggressive behaviors among animals, which may be within a species or between two different species, and may be a form of territoriality, dominance or mating strategy.

259. agraphia
Author: Mirrored from Guo Li's Dictionary of On-Line Medical Resources
Definition:

The inablity to write.

260. agriculture
Definition:

The science of raising plants and/or animals for food, clothing, or other useful products.

261. Agrobacterium tumefaciens
Definition:

Agrobacterium tumefaciens is a Gram-negative bacterium found in soil which causes crown gall disease in plants (which causes tumors to form at the crown and at the junction of the root and stem). The tumors are caused by the Ti plasmid in the bacterium; this plasmid is being heavily researched by plant genetic engineers because it is a useful way to introduce new genes into a plant cell.

262. agrochemical
Definition:

Term for any artificially-produced chemical (such as a feed additives, pharmaceutical, fertilizer or pesticide) used in agriculture to improve crop or livestock production.

263. agroforestry
Author: International Centre for Research in Agroforestry
Definition:

The collective word for all land-use systems and practices in which trees and shrubs are deliberately grown on the same land management unit as crops and/or animals. This can be either in some form of spatial arrangement or in a time sequence. To qualify as agroforestry, a given land-use system or practice must permit significant economic and ecological interactions between the woody and non-woody components. Within this broad definition, a wide variety of both traditional, as well as relatively new systems and practices, fall under the umbrella concept of agroforestry.

264. agroinfection
Definition:

A method of using the t-DNA of plasmids to infecting plant cells with DNA from a plant virus.

265. agronomy
Definition:

The scientific study of soil management and crop production.

266. AIDS (acquired immunodeficiency syndrome, HIV, human immunodeficiency virus)
Definition:

Acronym for Acquired Immunodeficiency Syndrome. An epidemic disease caused by an infection by human immunodeficiency virus (HIV-1), a retrovirus that causes immune system failure and debilitation and is often accompanied by cancers such as Kaposi's sarcoma as well as secondary infections such as tuberculosis. AIDS is spread through direct contact with bodily fluids.

267. AIDS-related complex (ARC)
Definition:

A set of symptoms, such as lymph node enlargement, fever, loss of weight, diarrhea, and minor opportunistic diseases associated with a weakened immune system, which indicates a less severe form of infection by the HIV virus than AIDS itself. In some cases this is diagnosed as a precursor to AIDS. Also known as "AIDS-related condition" or "AIDS-related syndrome".

268. alanine
Image: View the chemical structure
Author: Courtesy of MacMolecule
Definition:

One of the twenty naturally occurring amino acids. Has the following chemical characteristics:


pKa1   pKa2     pI      Water Solubility (30deg C)
2.35   9.69    6.02            15

269. alarmones
Definition:

Unusual dinucleotides, produced by bacteria under stress, which contain multiple phosphate groups between the two nucleotides.

270. albinism
Definition:

A rare genetic condition in which the body has no pigment whatsoever, due to an inherited inability to correctly manufacture melanin. This means that the animal with the condition (called an albino) has white, pale pink, or even translucent skin, white fur or hair, and pink eyes (no pigment in the iris means that the only color comes from the blood vessels in the eye).

271. albino
Definition:

1. An animal which has no pigment (melanin) whatsoever in its body. This means that its skin is white, pale pink, or even translucent, its fur (or hair) is white, and its eyes are pink (no pigment in the iris means that the only color comes from the blood vessels in the eye).
2. A plant which lacks part or all of its natural pigmentation or chlorophyll.

272. albumin
Definition:

A heat-coagulatable, water-soluble globular protein found in egg white, blood plasma and many other plant and animal tissues. Albumin from cow blood is often used as an enzyme stabilizer.

273. albuminuria
Definition:

More than normal amounts of a protein called albumin in the urine. Albuminuria may be a sign of kidney disease, a problem that can occur in people who have had diabetes for a long time.

274. alcohol
Definition:

An organic chemical containing one or more hydroxyl groups (-OH). Alcohols can be liquids, semisolids or solids at room temperature. Common alcohols include ethanol ("grain alcohol," the type found in alcoholic beverages) methanol (aka "wood alcohol," can cause blindness and other nervous system damage if ingested) and propanol.

275. alcohol
Author: Guo Li
Definition:

Ethyl alcohol, also known as ethanol, the spirit in wine, is classified as a sedative-hypnotic drug. The criminal code of Canada states that it is an offence while the person's ability to operate or has control of a motor vehicle or vessel is impaired by alcohol or a drug or while the person's blood levels of alcohol exceed 80 mg/dL.

Impaired driving performance has been observed with serum levels of ethanol as low as 30 mg/dL. A serum level above 300 mg/dL usually produces coma. Intoxication of alcohol is associated with violence, suicide, child and spouse abuse, respiratory depression, stupor, vomiting, predisposing to Mallory-Weiss Syndrome, hypoglycemia, cardiac arrhythmia, seizures. Chronic ingestion is associated with liver cirrhosis and withdrawal symptoms (Delirium Tremens).Two groups of alcohol drinkers are indentifiable based on the pattern of drinking: the problem drinkers and the ones with severe alcohol dependence.

Methyl alcohol, also known as methanol, or wood alcohol can also produce the sensation of being "drunk". However, ingestion of large quantities of methanol can cause visual disturbances (blindness via neurological damage), and a metabolic acidosis and is a medical emergency necessitating fluid resuscitation, respiratory care, ethanol infusion to block the building up of toxic products and dialysis.

Isopropyl alcohol is rubbing alcohol; it is poisonous.

276. Aldactazide
Author: Mirrored from Guo Li's Dictionary of On-Line Medical Resources
Definition:

A registered trademark drug combination of spironolactone and hydrochlorothiazide, for the treatment of high blood pressure.

277. aldehyde
Definition:

A carbon atom double-bonded to an oxygen, single-bonded to a hydrogen, and single-bonded to another chemical group (such as methane, benzene, another hydrogen, anything). The carbon oxygen double bond part is known as a carbonyl group (-C=O). An example is acetaldehyde, which is a carbonyl group single-bonded to a hydrogen and single-bonded to a methane (a methyl group: -CH₃).

278. aldicarb
Definition:

A colorless, water-insoluble, sulfur-containing chemical that is used as an insecticide and to kill nematode worms.

279. aldolase
Definition:

In glycolysis, aldolase is responsible for cleaving fructose 1,6-bisphosphate into two 3-carbon molecules, dihydroxyacetone and glyceraldehyde 3-phosphate. This is done via the formation of a protonated Schiff base at a specific lysine residue.

280. Aldoril
Author: Mirrored from Guo Li's Dictionary of On-Line Medical Resources
Definition:

A registered trademark drug combination of methyldopa and hydrochlorothiazide, for the treatment of high blood pressure.

281. aldose
Definition:

Any monosaccharide sugar that contains an aldehyde group (-CHO).

282. aldose reductase inhibitor
Author: PharmInfoNet
Definition:

A class of drugs being studied as a way to prevent eye and nerve damage in people with diabetes. Aldose reductase is an enzyme that is normally present in the eye and in many other parts of the body. It helps change glucose (sugar) into a sugar alcohol called sorbitol. Too much sorbitol trapped in eye and nerve cells can damage these cells, leading to retinopathy and neuropathy. Drugs that prevent or slow (inhibit) the action of aldose reductase are being studied as a way to prevent or delay these complications of diabetes.

283. aldosterone (aldocortin)
Image: View the chemical structure
Definition:

A steroid hormone that is produced by the adrenal cortex and mainly functions to regulate chloride, potassium, and sodium metabolism. Abnormally high levels of this hormone cause symptoms such as sodium retention, high blood pressure, heartbeat irregularities and possibly paralysis.

284. aldrin
Image: View the chemical structure
Definition:

A chlorinated organic insecticide whose use and manufacture has been banned in the U.S. (but not all other contries have followed suit). The chemical can poison via skin contact, ingestion or inhalation; symptoms include kidney damage, shaking, slurred speech, convulsions, respiratory failure, and death. Chronic exposure to non-lethal doses of aldrin can cause liver damage and probably cancer.

285. aleurone (aleuron)
Definition:

These are granules of protein found in the top cell layer of the endosperm of grains such as wheat.

286. alevin (sac fry, yolk-sac fry)
Author:
Definition:

In fisheries terminology, a larval salmonid that has hatched but has not fully absorbed its yolk sac, and generally has not yet emerged from the spawning gravel. Absorption of the yolk sac, the alevin's initial energy source, occurs as the larva develops its mouth, digestive tract and excretory organs and otherwise prepares to feed on natural prey.

287. alfisols
Author:
Definition:

Soils having significantly more clay in the B-horizon than in the A-horizon and high base status.

288. algae
Definition:

This is a large group of diverse unicellular and multicellular aquatic plants; they grow in both fresh water and seawater and are used commercially as a source of thickeners (agar, agarose, algin, carrageenan) and pigments such as beta carotene. Some countries harvest them as food; Spirulina is produced by Israel and Mexico, and the Japanese consume some species of Chlorella. Some species of algae are important commercial pests because they clog pipes and foul pools and reservoirs.

289. algal oxidation pond
Definition:

A wide, shallow pond used in wastewater treatment; the algae produce oxygen so that bacteria can aerobically digest sewage in the water.

290. algicide
Definition:

Any chemical that kills algae.

291. algin (alginate)
Definition:

This gelatinous material, a polysaccharide extract from brown algae, is widely used in foods, medicines, and industrial and household products. The main algae that produce it are Laminaria species and Macrocystis pyrifera (a chemically different version of algin is produced by the bacterium Azobacter vinelandii.)

292. alicyclic
Definition:

This refers to any aliphatic compound that contains a ring of carbon atoms.

293. aliphatic
Definition:

A major class of organic compounds where carbon and hydrogen molecules are arranged in straight or branched chains. A type of hydrocarbon. Includes alkanes, alkenes, and alkynes.

294. aliquot
Definition:

The division of a sample of a substance into equal parts, each of which representing a known quantitative relationship to each other and to the sample as a whole.

295. alkali metal
Definition:

Any of the highly reactive metals (such as sodium or potassium) found in the first column of the periodic table; these metals act as bases.

296. alkali sink
Author:
Definition:

A land basin in which water evaporation produces high salt concentrations that may, or may not, support salt marsh vegetation.

297. alkaline
Author: Mirrored from Tsute Chen's Glossary of Microbiology
Definition:

A base; a compound whose water-based solutions have a pH higher than 7, a bitter taste, a slippery feel in water, turn red litmus paper blue, and can react with acids to form salts.

298. alkaline earth
Definition:

Any of the metallic elements found in the second column of the periodic table, such as calcium and magnesium.

299. alkaline phosphatase
Definition:

An enzyme which hydrolyzes phosphate esters and works best in the pH range of 9 to 11; it catalyzes the removal of phospate groups near the 5' end of linear DNA strands such as restricted plasmid molecules. This enzyme is typically obtained from calf intestinal tissue or E. coli and is used widely in gene cloning experiments and in enzyme-antibody conjugates in ELISA and immunochemistry.

300. alkaline phosphatase (ALP)
Author: Guo Li
Definition:

This is an enzyme that is produced by liver cells lining the collecting system (Kupffer's cells). Its level is elevated in conditions of obstruction of biliary collecting system (such as by cancer and gallstones), cirrhosis of liver and bone growth, infarcting bowel, and metastatic tumor to bone.

Normal range: 50-190 IU/L; in children it can be up to 300 IU/L

301. alkaline proteases
Definition:

These proteases work best in the pH range of 8 to 11 and are used widely in washing powders and to de-hair hides. Alkaline proteases are mainly produced by bacteria in the Bacillus species.

302. alkalinity
Author:
Definition:

Measure of the power of a solution to neutralize hydrogen ions (H+), usually expressed as the equivalent concentration (mg/L) of calcium carbonate (CaCO₃).

303. alkaliphile (alkalophile)
Author: Mirrored from Tsute Chen's Glossary of Microbiology
Definition:

An organism that grows optimally at high pH (alkaline conditions). The typical pH range for alkaliphiles is 8 - 11. They grow poorly or not at all at a pH below 7. Compare with acidophile.

304. alkaloids
Definition:

A class of over 3000 known nitrogen-containing compounds (such as morphine, caffeine, cocaine and nicotine) that are typically basic (pH over 7) and are produced by plants but have strong physiological effects on animals (including humans). They are synthesized from amino acid precursors such as tryptophan and tyrosine.

305. alkalophile (alkalinophile, basophile)
Definition:

A microorganism which grows best in alkaline, or basic, environments, where the pH is between 7 (neutral) and 12.

306. alkalosis
Definition:

A metabolic illness caused when the body's ability to buffer hydroxide (OH^-) ions is compromised, typically causing a rise in blood pH (the blood becomes more basic). Compare acidosis.

307. alkane (paraffin)
Definition:

An organic molecule containing carbon and hydrogen atoms in straight or branched chains, where all of the carbon-carbon bonds are single bonds. One of three major classes of aliphatic hydrocarbons.

308. alkaptonuria (dark urine disease)
Definition:

This illness, caused by a recessive gene that causes a deficiency of the enzyme homogensitic acid deoxygenase, was the first recognized genetic disease. It is characterized by abnormal deposits in the connective tissue and urine which turn dark when exposed to air. Severe arthritis and blockages in arteries and heart valves can occur in later stages of the disease. Its incidence is about one in a million.

309. alkene (olefin)
Definition:

An organic molecule containing carbon and hydrogen atoms in straight or branched chains, where at least one carbon-carbon bond is a double bond. One of three major classes of aliphatic hydrocarbons.

310. alkyl group
Definition:

A funtional group on an organic molecule which is derived from an alkane which has lost a hydrogen atom.

311. alkylating agent
Definition:

A substance which contains an alkyl (derived from an alkane) radical, with which it can replace a hydrogen atom with itself in an organic compound. As a result, it can act on DNA and interfere with replication, making it useful for destroying cells such as cancer cells.

312. alkyne (acetylene)
Definition:

An organic molecule containing carbon and hydrogen atoms in straight or branched chains, where at least one carbon-carbon bond is a triple bond. One of three major classes of aliphatic hydrocarbons.

313. all-or-nothing phenomenon
Definition:

1. Refers to the phenomenon where the strength of a nerve impulse is not dependent on the strength of the stimulus. Instead, there is a threshold level of stimulus strength that must be reached before the nerve will fire an impulse (at full capacity). Below the threshold, the nerve will not fire at all.
2. In cardiology, it refers to the same phenomenon observed in the heart muscle, which will either contract fully or not at all.
3. In studies of behavior, it refers to the same phenomenon where a behavioral stimulus will either produce a complete response or no response at all.

Also called all-or-nothing principle, all-or-none law, all-or-none responsiveness, etc.

314. allantoin
Definition:

Any of many nitrogen-containing organic compounds which are found in some plants and in the urine of some mammals. Allantoin is used to treat wounds and ulcers.

315. alleles
Definition:

Alternative forms of a genetic locus; a single allele for each locus is inherited separately from each parent (e.g., at a locus for eye color the allele might result in blue or brown eyes).

316. allelochemicals
Author: Mirrored from Dave Sutton's Aquatic Plant Glossary
Definition:

Compounds that have an allelopathic effect.

317. allelopathy
Author: Mirrored from Dave Sutton's Aquatic Plant Glossary
Definition:

The influence or effect of one living plant upon another; refers to biochemical interaction between all types of plants and its effect depends on a chemical compound being added to the environment.

318. allergen
Definition:

Something which can cause an allergic reaction. For example, ragweed pollen is the allergen which causes hay fever.

319. allergist
Definition:

A doctor who specializes in treating allergies.

320. allergy
Author: Mirrored from Tsute Chen's Glossary of Microbiology
Definition:

A harmful immune reaction, either immediate-type or delayed-type hypersensitivity caused by a foreign antigen (i.e. allergen) in food, pollen, or chemicals. In most cases the cause of the allergy is otherwise harmless to the body.

321. allied health
Definition:

This term refers to a wide range of health professionals who are not physicians; it encompasses occupations such as clinical lab technicians, emergency medical technicians (EMTs), occupational therapists, physical therapists, medical assistants, physician assistants, health physicists, and medical technicians. Many of these occupations require a specialized 4-year undergraduate degree; some, like physicians assistants, may need a master's degree. Some people consider nurses to fall in this category; others categorize them separately.

322. alligators
Definition:

One of two species of crocodilian reptiles, distinguished from other caymans by a long snout, and teeth which can be seen when the mouth is closed. While the popular name (from the Spanish "lagarto", for lizard) is often applied to all American crocodilians, only Alligator mississippiensis, and its Chinese counterpart, are true alligators.

323. allochthonous
Author:
Definition:

Derived from outside a system, such as the leaves of terrestrial plants that fall into a stream. Compare autochthonous.

324. allogamy (adj. allogamous)
Author: ForBio Ltd.
Definition:

Synonym for cross-fertilization; this is the combining of gametes derived from different individuals.

325. allogeneic transplant
Definition:

A transplant of an organ or tissue that is donated either by a genetically matched relative of the patient or by an unrelated (but genetically similar) donor.

326. allograft (allogenic graft, homograft, homoplastic graft)
Definition:

Tissue transplantation between genetically dissimilar members of the same species.

327. allograft immunity (transplant rejection, homograft rejection)
Definition:

The recipient's immune system rejects tissue grafted from a genetically dissimilar donor (of the same species) and stages an immune attack against it.

328. alloimmune
Definition:

Indicates or refers to an organism's being immune to proteins, cells, or other antigens from members of its own species.

329. alloimmunization
Definition:

The process of an organism becoming immune to proteins, cells, or other antigens from members of its own species.

330. alloimmunization
Definition:

Immunization against allogenic antigens; immunization against substances that can provoke an immune system response which are produced by genetically dissimilar members of the same species.

331. allopatric
Definition:

Relating to or involving two populations of the same species which cannot interbreed because they are separated by a geographic barrier (such as a mountain range or wide river).

332. allopatric speciation (geographic speciation)
Definition:

The evolutionary process through which two geographically separated (and therefore non-interbreeding) populations of the same species become less and less similar to each other over time (via mutation or the success of different traits in each environment) and eventually become distinctly different species.

333. allopatrically
Definition:

An adverb refering to a specific mechanism of evolutionary divergence. A species which arose allopatrically from another diverged from the other because of evolutionary changes occurring in two different geographically separated populations. Also see allopatric and speciation.

334. allopatry
Definition:

The condition of two populations of the same species being separated by a geographic barrier that prevents them from interbreeding.

335. allopolyploid
Definition:

A hybrid, usually a plant, which is created from two closely-related species and contains one or more extra sets of chromosomes (i.e. if each parent normally has two sets, the hybrid may have four). See polyploid.

336. allopurinol
Definition:

An organic molecule used to treat gout and certain blood disorders by preventing excessive amounts of uric acid from building up in the blood. Formula: C₅H₄N₄O. It is a derivative of the purine base hypoxanthine, and inhibits the enzyme xanthine oxidase.

337. allosteric
Author: Mirrored from Tsute Chen's Glossary of Microbiology
Definition:

Used to describe some protein, especially an enzyme, in which a compound combines with a site on the protein other than the active site. This may result in a conformational change at the active site so that the normal substrate cannot bind to it. The allosteric property is useful in the regulation of enzyme activity.

338. allosteric enzyme
Definition:

A regulatory enzyme whose activity is modified by the noncovalent binding of a particular metabolite at a site (the allosteric site) other than the active site.

339. allostery
Definition:

A phenomenon in which a small ligand binds to a receptor site on a protein, changes the shape of the protein and thus changes the specificity of a second site (either another receptor or an enzyme active site) on that protein.

340. allotetraploid hybrid (amphidiploid)
Definition:

A hybrid, usually a plant, of two different species which has two sets of chromosomes from each of the parent species. Also see allopolyploid.

341. allotrope
Definition:

Any individual structural form of an element which comes in at least two different structural types.

342. allotropes
Definition:

Different versions of the same chemical element which have dissimilar chemical and physical properties; for instance, graphite and diamonds are both versions of carbon, but they have very different properties.

343. allozyme
Author: ForBio Ltd.
Definition:

An isozyme which differs from other variants of the enzyme as result of an allelic difference.

344. alluvial
Definition:

1. Relating to something in streams and rivers or created/deposited by stream action.
2. Describes materials deposited by running water.

345. alluvium
Author:
Definition:

1. Material deposited by running water, including the sediments laid down in riverbeds, flood plains, lakes and estuaries.
2. Deposit of stream-borne materials in and along a channel.

346. aloe vera
Definition:

A succulent, fibrous plant, of the family Liliaceae, with basal leaves, having toothed or fibrous margins. Native to southern Africa, it is a popular ornamental, and its juice is used alone or in preparations to soothe minor burns and skin irritations.

347. alopecia
Definition:

Clinical term meaning loss of hair.

348. alpha amanitin
Definition:

An antibiotic derived from the Amanita mushroom which acts by interfering with the function of RNA polymerase.

349. alpha cell
Author: PharmInfoNet
Definition:

A type of cell in the pancreas (in areas called the islets of Langerhans). Alpha cells make and release a hormone called glucagon, which raises the level of glucose (sugar) in the blood.

350. alpha fetoprotein (AFP)
Definition:

This is a protein the blood level of which is measured by laboratory methods. Its level is elevated in the mother's blood when there are fetal spinal cord defects (anencephaly, myelomeningocele), threatened abortion, twin gestation, and abruptio placentae. The AFP screening test for the mother's blood is usually conducted at 16 - 18 weeks of pregnancy. AFP level in the amniotic fluid obtained in amniocentesis is measured to identify abnormal fetal development.

In humans, AFP is a useful marker for the diagnosis and assessment of the tumors of the testis (teratocarcinoma and embryonal carcinoma). AFP is also elevated in patients with primary liver cancer (hepatocellular carcinoma) and in women with some types of germ cell ovarian tumors.

Normal range: less than 40 micrograms per liter.

351. alpha glucosidase
Definition:

An enzyme which removes the last 1,4-linked alpha-D-glucose residue from the nonreducing end of a long chain (or polymer) of such residues, making an alpha-D-glucose molecule out of it in the process.

352. alpha helix
Definition:

This helical, usually right-handed arrangement of a polypeptide chain is a common secondary structure in proteins. The helix has maximal intrachain hydrogen bonding.

353. alpha ketoglutarate dehydrogenase
Definition:

This is an enzyme that acts in the alpha-ketoglutarate pathway, an intermediate pathway in the Krebs cycle in which amino acid derivatives enter the cycle. Alpha ketoglutarate dehydrogenase serves to convert NADH + succinyl-CoA + CO₂ into alpha-ketoglutarate + CoA + NAD⁺.

354. alpha particle
Definition:

A radioactive particle made up of two protons and two neutrons; these particles are created by the decay of a radioactive material or by nuclear bombardment, and they are the same as the nucleus of a helium-4 atom.

355. alpha radiation (alpha ray)
Definition:

The most easily-absorbable type of radiation; it consists of a stream of alpha particles, doubly ionized helium nuclei which are electrically charged and produce intense ionization in matter. Alpha radiation can be deflected in electromagnetic fields.

356. alpha thalassemia
Definition:

One of two major types of thalassemia, a genetically inherited disease, in which one of the two types of polypeptides making up the hemoglobin protein is defective or missing. Hemoglobin proteins are composed of four polypeptides -- two "alpha chains" and two "beta chains". In alpha thalassemia, the alpha chains are defective or missing (see also beta thalassemia). This disease mainly affects individuals of Southeast Asian, Chinese, and Filipino ancestry; in its most severe form it results in the death of the fetus or newborn. Individuals with less severe cases have varying degrees of anemia.

357. alpha thalassemia
Author: Guo Li
Definition:

This form of thalassemia is due to gene deletion, which causes reduced alpha-chain synthesis.

358. alpha viruses
Definition:

These are the major viruses in the Togavirus group and include eastern and western equine encephalitis viruses, the Sindbis virus and the Semliki Forest virus. The last two viruses are being researched as vectors for expressing heterologous genes.

359. alpha-fetoprotein
Definition:

The fetal equivalent of albumin.

360. alpha1-antitrypsin
Author: Guo Li
Definition:

This is a protease inhibitor (Pi). Low serum levels of this antienzyme predisposes patients to early onset of emphysema and chronic liver disease. Ten percent of the adult population has the heterozygote genotype MZ in which intermediate levels of alpha1-antitrypsin is present. The incidence of liver disease in MZ is only mildly higher than the general population.

Normal ranges by genotype:


normal MM: more than 250mg/deciliter
heterozygous MZ: 50 - 250 mg/dL
homogygous ZZ: less than 50 mg/dL

361. Alport's syndrome (Alport syndrome)
Author: Guo Li
Definition:

Alport's syndrome consists of progressive nephritis, nerve deafness, leading to kidney failure in the second to third decades of life. Autosomal dominant, autosomal recessive, and X-linked inheritance are noted.

362. alprazolam (Xanax)
Definition:

This is a prescription drug used to treat anxiety. It is a central nervous system depressant, and can therefore have a negative impact on coordination and mental alertness. Side effects typically include drowsiness and/or mood changes.

363. alternate
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

Of leaves or other lateral plant organs, borne singly at different heights on the axis; of floral parts, on a different radius, e.g. describing the position of stamens with respect to petals. Compare opposite.

364. alternation of generations
Author: Mirrored from Dave Sutton's Aquatic Plant Glossary
Definition:

The occurrence in one life history of two or more different forms differently produced, usually an alternation of a sexual with an asexual form.

365. alternative mRNA splicing
Definition:

Splicing different exons in or out of messenger RNA to form different mRNA transcripts.

366. Alu sequence
Definition:

Any of a family of short (300 base pairs long) repeated sequences that occur throughout the human genome.

367. alveola
Author: Mirrored from Dave Sutton's Aquatic Plant Glossary
Definition:

A pit on the surface of an organ.

368. Alzheimer's disease
Author: Guo Li
Definition:

Alzheimer's disease is a form of senile dementia of unknown origin that has characteristic pathologic changes in the brain. Its onset is slow and at an earlier age than the common dementia. After onset, it progresses steadily and the pathology is more severe than the average form of senile dementia. Most studies report that this disease is responsible for the cognitive decline in about 50% of demented older adults.

369. Alzheimer's disease (AD)
Author: The Alzheimer's Association
Definition:

A progressive, neurodegenerative disease characterized by loss of function and death of nerve cells in several areas of the brain leading to loss of cognitive function such as memory and language. The cause of nerve cell death is unknown. Alzheimer's disease is the most common cause of dementia.

370. amantadine (Symmetrel)
Definition:

This prescription drug is used to treat Parkinson's syndrome; it is believed to work by releasing dopamine from nerve endings. This drug should not be taken by pregnant women or by nursing mothers. It can cause side effects such as nausea, dizziness, insomnia, depression and other mood problems.

371. amber codon
Definition:

The nonsense codon UAG, one of three codons which, instead of coding for an amino acid, signals that the translation of mRNA into a chain of amino acids should stop.

372. amber mutation
Definition:

A mutation from a codon which codes for an amino acid into the amber codon UAG, which normally signals that the translation of mRNA into an amino acid chain should stop. The mutation causes the amino acid chain to stop forming before it is actually completed.

373. amber suppressor
Definition:

A tRNA molecule which suppresses amber mutations because it has mutated to recognize the amber codon UAG (which normally signals that the translation of mRNA into an amino acid chain should stop) as a signal for inserting whatever amino acid it carries into the chain. As a result, it can prevent the amino acid chain from ending before it is completed.

374. ambident anion
Definition:

A group of atoms that carry an overall negative charge and which can donate electrons to electron acceptors such as metal atoms.

375. ambident ligand
Definition:

A ligand that can donate electrons through two or more atoms on their molecule.

376. ambient
Definition:

Describes the surrounding environment (especially temperature and pressure) of an object or experiment, in particular an environment which affects the object or experiment but is not affected by it.

377. ambiguous codon
Definition:

A codon that codes for more than one amino acid.

378. ambisense expression strategy
Definition:

The coding of viral proteins in both the sense (coding) and antisense (noncoding) strands of complementary mRNA, so that the viral proteins are produced no matter which strand gets translated.

379. amboceptor
Definition:

An antibody which can combine both with a cellular antigen(such as a virus or bacterium) and with a complement because it has two combining elements.

380. ambulatory
Definition:

An organism which is able to move from place to place, and is not stationary. Most often the term is used to describe organisms which can walk.

381. ameba (amoeba)
Definition:

A common name describing the one-celled organisms classified under the order Amoebida of the class Sarcodina. An ameba has a constantly changing form and moves and eats by extending pseudopods, or long fingers of itself, from its body cytoplasm.

382. amebiasis (amebic dysentery)
Definition:

Amebiasis is an infection with amoebas (a type of protozoan), particularly Entamoeba histolytica. The disease is contracted by eating food or drinking water that has been infected with encysted forms of the amoebas. The symptoms include diarrhea, weakness, and sometimes jaundice. During the course of the disease, sores and abscesses form on the mucous membrane of the large intestine (sometimes causing perforations), and the abscesses may be carried to the liver via the portal vein. Patients are usually treated with drugs called metronidazole (Flagyl) and chloroquinine; they may need to be medicated for up to three months to clear the infection.

383. amebic dysentery (amoebic dysentery)
Definition:

A disease caused by the parasitic amoeba Entamoeba histolytica. Symptoms include vomiting, nausea, severe diarrhea, abdominal pain, and ulcers (especially in the colon).

384. amebicide
Definition:

A substance which is destructive to, or used to kill amebas.

385. ameiosis
Definition:

A form of nuclear division which does not reduce the number of chromosomes because both of the nuclear divisions normally part of the process of meiosis have failed to occur.

386. ameloblast
Definition:

A cell which plays a role in the development of tooth enamel during the development of the tooth.

387. ameloblastoma (adamantinoma)
Definition:

A malignant jaw tumor which stems from the ameloblasts, cells which form tooth enamel.

388. amenorrhea
Definition:

The absence of, or the abnormal stoppage of, menstruation. "Primary amenorrhea" is when menstruation fails to begin at puberty. "Secondary amenorrhea" is when menstruation stops occuring after the menstrual cycle has begun.

389. amensalism (adj. amensal)
Definition:

A type of symbiosis where two (or more) organisms from different species live in close proximity to one another, where one of the members suffers as a result of the relationship while the other is unaffected by it.

390. Ames test
Definition:

A bacterial test for mutagenic carcinogens.

391. amethopterin (amethopterine, methotrexate)
Image: View the chemical structure
Definition:

A drug which inhibits the proliferation of cancer cells. It is used mainly to treak leukemia, but is also used to suppress the immune systems of transplant patients and to treat psoriasis.

392. amide
Definition:

1. An organic compound which contains a -CONH₂ group.
   
2. Any of the organic compounds produced when a hydrogen atom of ammonia (NH₃) is replaced with a metal.

393. amide linkage
Definition:

This is a carboxylic acid containing an amino group (-NH2). In an alpha amino acid, the amino group is attached to the carbon atom directly beside the carboxyl group.

394. amine
Definition:

1. Any of the organic compounds produced when one or more hydrogen atoms of ammonia is replaced with organic groups.
2. When used as a suffix in a long name for an organic molecule (i.e. "-amine" in "glutamine"), it indicates the presence of an -NH₂ group.

395. amino acid
Definition:

Any of a class of 20 molecules that are combined to form proteins in living things. The sequence of amino acids in a protein and hence protein function are determined by the genetic code.

396. amino group
Definition:

An -NH2 group. Organic compounds which have this group are called amines.

397. amino sugar
Definition:

A monosaccharide in which one or more of its hydroxyl groups has been replaced with an amino group.

398. amino sugars
Definition:

A monosaccharide, or simple sugar, which has been modified into an amine by the replacement of a hydroxyl group (an -OH group) with an amino group (an -NH2 group).

399. amino terminal (amino terminus)
Definition:

The end of a polypeptide chain with the unattached amino group (-NH2 group). Each amino acid in the chain has an amino group on one side (which is attached to the carboxyl group (a -COOH group) of the previous amino acid) and a carboxyl group on the other side (which is attached to the amino group of the next amino acid). The other end of the polypeptide chain is called the carboxyl terminal.

400. amino-terminal residue
Definition:

The only amino acid residue in a polypeptide chain that has a free alpha-amino group; it defines the amino terminus of the polypeptide.

401. aminoacyl-tRNA
Definition:

The name of the complex created when a tRNA molecule is attached to its specific amino acid and ready to participate in protein synthesis.

402. aminoglycoside antibiotics
Definition:

A group of antibacterial drugs (such as kanamycin, neomycin and streptomycin) which are mostly produced by fungi and which contain an amino sugar, and amino- or guanido-substituted inositol ring, and other sugar residues. They are all broad-spectrum antibiotics that inhibit bacterial protein synthesis by binding to their ribosomes. However, all these drugs are toxic to humans and aren't used except in special situations.

403. aminoglycoside-3'-phosphotransferase (APH)
Definition:

A bacterial enzyme which confers resistance to the antibiotic neomycin.The APH gene is used as a selectable marker in genetic experiments, whereby bacterial cells which do not have the gene are eliminated from a population and thus selected against when exposed to neomycin.

404. aminopeptidase
Definition:

This is an enzyme that sequentially cuts (via hydrolysis) the peptide bonds from the N-terminus of a chain of polypeptides. This sort of enzyme is known as an exopeptidase.

405. aminophylline
Author: Guo Li
Definition:

This is a drug for the treatment of asthmatic attacks by relieving the constriction of the airways. It is delivered intravenously.

406. aminotransferase (transaminase)
Definition:

An enzyme that catalyzes the conversion of amino groups from alpha-amino to alpha-keto acids.

407. amitriptyline (Elavil, Endep)
Definition:

This is a prescription drug used to treat depression (it is classed as a tricyclic antidepressant). It may cause a wide range of side effects, including rashes, nausea, weight gain/loss, drowsiness, nervousness, insomnia, confusion, seizures, coma, etc.

408. ammonia
Definition:

1. The common name for NH₃, a strongly basic, irritating, colorless gas which is lighter than air and readily soluble in water. It is formed in nature as a by-product of protein metabolism in animals. Industrially, it is used in explosives, fertilizer, refrigerants, household cleaning solutions, etc.
2. Ammonium hydroxide (NH₄⁺), a solution of ammonia gas in water.

409. ammonium sulfate precipitation
Definition:

In this technique, ammonium sulfate is used to make proteins precipitate out of a solution; the proteins are then collected by centrifugation.

410. ammonotelic
Definition:

Medical term meaning excreting excess nitrogen as ammonia instead of uric acid.

411. amnesia
Author: Guo Li
Definition:

This is the condition in which one's memory is lost due to disease or psychological or physical trauma.

412. amniocentesis
Definition:

A technique for testing the genetic health of a fetus by inserting a needle through the mother's abdominal wall into the uterus and extracting a small amount of the amniotic fluid, the fluid that surrounds the fetus. Sloughed-off fetal cells (fibroblasts) found in this fluid are then cultured and their DNA examined for defects. This procedure is done in the second trimester, and because of the time needed to do the culture, results aren't generally available until after the 20th week of pregnancy.

413. amniocyte
Definition:

A cell found floating freely in the amnion sac (a membranous sac containing the amniotic fluid) surrounding an embryo.

414. amniotic caruncle
Author: Guo Li
Definition:

An amniotic caruncle is a small red fleshy swelling of epithelial origin which is occassionally found at the placental insertion of the umbilical cord.

415. Amoeba
Author: Mirrored from Tsute Chen's Glossary of Microbiology
Definition:

A genus of free-living amoebae. Type species: Amoeba proteus.

416. amoeboid
Author: Mirrored from Tsute Chen's Glossary of Microbiology
Definition:

Amoeba-like.

417. amoeboid movement
Author: Mirrored from Tsute Chen's Glossary of Microbiology
Definition:

A type of motility in which cytoplasmic streaming extrudes outward of the cell to form pseudopodia so that the cell can be relocated.

418. amorph
Definition:

1. A gene which is inactive. Thus, an "amorphic" gene.
2. Something that lacks a discernible shape and thus can be describes as "amorphous."

419. amorphic allele
Definition:

An allele which is genetically inactive.

420. amorphous
Definition:

Having an irregular or undefined shape or structure.

421. amoxapine (Asendin)
Definition:

This prescription drug is used to treat depression (it is a tricyclic antidepressant of the dibenzoxazepine class.) It may cause tardive dyskinesia in some people, and it causes a wide range of side effects. Patients may suffer withdrawal symptoms if they stop taking this drug abruptly.

422. amoxicillin
Author: Guo Li
Definition:

This is an antibiotic of the penicillin class. It is related closely to ampicillin but is better absorbed in the intestines.

423. amperometric
Definition:

Refers to any type of chemical analysis that involves using electrical currents.

424. amphibian
Definition:

This refers to a class of vertebrate animals that spend part of their time on land and part in the water; they are an intermediate form between fishes and reptiles. Amphibians must return to the water to breed and they have distinct larval and adult forms. Members of this class include frogs, toads, and salamanders.

This word is derived from the Greek word amphibios, which means "living a double life".

425. amphibolic
Definition:

A metabolic pathway that can both create and destroy metabolites (that is, it is both anabolic and catabolic). Such an intermediate pathway allows using the breakdown products from one pathway as the substrates, or ingredients, for a compound in another pathway.

426. amphidromous
Author:
Definition:

Moving from fresh water to the sea, or vice versa, for nonreproductive purposes such as feeding.

427. amphipathic
Definition:

Refers to a biomolecule that has both polar and nonpolar domains.

428. amphiprotic
Author: Roger Sinclair
Definition:

A molecule or ion that can act as an acid (donate a proton) or gain a proton (act as a base).

429. ampholyte
Definition:

An amphoteric electrolyte. Such a molecule carries a net charge that varies according to the pH of its surroundings until, at a specific pH, its net charge is zero (isoelectric point).

430. amphoteric
Definition:

Refers to a molecule or atom that is capable of accepting or donating protons and thus can serve as an acid or a base.

431. amphotericin
Definition:

One of two antifungal antibiotics:
1. Amphotericin A: The less active form of the antibiotic produced by the bacteria Streptomyces nodosus. It is not used clinically.
2. Amphotericin B: An antibiotic produced by the bacteria Streptomyces nodosus which is used to treat a wide variety of fungal infections. Formula: C₄₇H₇₃NO₁₇.

432. amphotericin B
Author: Guo Li
Definition:

This is a potent anti-fungal drug. Its route of administration is usually by intravenous injection for severe and life-threatening body infection, aerosol for lung fungal infection and irrigation of the bladder. This drug has many frequently and severe side effects. It is poorly eliminated by the body and therefore should be used as a last resort.

433. amphotropic packaging cell lines, amphotropic virus
Author: Jim Embree
Definition:

Clonal entities that express genes or act as viral vectors that infect cell lines to stably infect and then express genes of choice.

434. ampicillin
Image: View the chemical structure
Definition:

An antibiotic that is basically penicillin to which an amino group has been added to make the drug more versatile. Ampicillin works by inhibiting bacteria's ability to grow cell walls.

435. amplexicaul
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

Of a leaf base: stem-clasping.

436. amplicon
Definition:

A term for any small, replicating DNA fragment.

437. amplification
Definition:

An increase in the number of copies of a specific DNA fragment; can be in vivo or in vitro. See also: cloning, polymerase chain reaction.

438. Amplified Fragment Length Polymorphism (AFLP)
Author: Sander Voormolen
Definition:

Invented by KeyGene, a Dutch biotech company based in Wageningen, Holland The technique is now merchandised under licence agreement by Perkin Elmer. Selected markers are amplified in a PCR, which makes AFLP an easy and fast tool for strain identification in agriculture, botany, microbiology and animal breeding.

439. ampulla of Vater
Definition:

A nipple-like outgrowth in the duodenum (upper part of the small intestine) that marks the entry of the biliary and pancreatic ducts.

440. amputation (adj. amputate)
Author: Guo Li
Definition:

This is the procedure in which a limb is surgically removed.

441. amylase
Author: Guo Li
Definition:

Amylase is secreted by the acinar cells of the pancreas and is measured from blood samples. It is elevacted in pancreatitis, trauma to the bowel, and mumps infection.

Normal range: 29 to 220 IU/L.

442. amylase
Definition:

There are two commercially-used forms of this starch-hydrolyzing enzyme:
• alpha amylase breaks the alpha-1,4-glucosidic bonds of starch to yield oligosaccharides. Slightly different versions of this enzyme are produced by the bacteria Bacillus amyloliquefaciens, B. licheniformis, B. subtilis and the fungus Aspergillus oryzae. Alpha amylase is used to make corn syrup, beer, wallpaper removers, cold-soluble laundry starch, and digestive aids.
• beta amylase has exo-alpha-1,4-glucanase activity and acts on linear alpha-1,4-linked glucans, breaking alternate bonds to form maltose. This enzyme is found in most plants but is rare in fungi and bacteria; it is the amylase produced by germinating barley, which is used in beer production.

443. amyloidosis
Author: Guo Li
Definition:

This is a condition in which a person's organ function is impaired by deposits of protein fibrils or proteins complexed with polysaccharides. The symptoms are that of failure of the affected organs. Study of tissue samples (biopsy) definitively confirms the diagnosis.

444. amylose
Definition:

One of two types of glucose polymers that together make up starch. (Amylopectin is the other type.) Amylose is the portion of starch that is soluble in water. The chemical structure of amylose is very similar to that of cellulose.

445. amyotrophic lateral sclerosis
Author: Guo Li
Definition:

This is the most frequent form of the progressive nerve disorders affecting the brain, brain stem and spinal cord, usually appearing when a person is 50-70 years old. It is sometimes associated with dementia and Parkinson's disease.

446. amyotrophy
Author: PharmInfoNet
Definition:

A type of diabetic neuropathy that causes muscle weakness and wasting.

447. anabolic pathway
Definition:

A reaction or series of reactions in a metabolic pathway that synthesize complex molecules from simpler ones, usually requiring the input of energy.This is the opposite of a catabolic pathway.

448. anabolism
Definition:

A stage of intermediary metabolism in which cell components are synthesized from smaller precursor molecules; anabolism is a process that requires energy.

449. anadromous
Author:
Definition:

Moving from the sea to fresh water for reproduction.

450. anadromous fish
Author:
Definition:

Anadromous fish means fish which spawn in fresh water and spend a portion of their lives in the ocean.

451. anaerobe
Definition:

A microorganism that either does not require oxygen or actually cannot live in the presence of oyxgen.

452. anaerobic
Definition:

Relating to a process that occurs with little or no oxygen present.

453. anaerobic digester (anaerobic bioreactor)
Definition:

This is a bioreactor for anaerobically digesting sewage-laced wastewater. In it, anaerobic bacteria produce a mix of methane and carbon dioxide; as much as 90% of the chemical energy in the wastewater can be converted to methane, which is typically exhausted continuously and collected for use as a fuel or for a reagent for other industrial chemical reactions.

454. anaerobic respiration
Author: Mirrored from Tsute Chen's Glossary of Microbiology
Definition:

Respiration under anaerobic conditions. The terminal electron acceptor, instead of oxygen in the case of regular respiration, can be: CO2, Fe2+, fumarate, nitrate, nitrite, nitrous oxide, sulphur, sulphate, etc. Note that anaerobic respiration still uses the electron transport chain to dump the electron while fermentation does not.

455. anaerobiosis
Author: Mirrored from Dave Sutton's Aquatic Plant Glossary
Definition:

1. Life in the absence of air or free oxygen.
2. Anaerobic respiration, respiration occurring in the absence of oxygen.

456. anaerogenic
Author: Mirrored from Tsute Chen's Glossary of Microbiology
Definition:

Without forming gas, e.g., anaerogenic fermentation.

457. analeptic
Definition:

Describes a drug that has a restoratative or stimulating effect, typically on the central nervous system.

458. analgesia
Definition:

Loss of normal sensitivity to pain; compare anesthesia.

459. analgesic
Definition:

A drug used to relieve pain.

460. analogy (adj. analogous)
Definition:

Two anatomical structures or behavioral traits within different and unrelated organisms which perform the same functions in each organism but which did not originate from an ancestral structure or trait that the organisms' ancestors had in common. Instead, the structures or traits arose separately and then later evolved to perform the same function (or similar functions). See also convergent evolution. Compare homology.

461. analyte
Definition:

The substance being measured in an analytical procedure.

462. anamorph
Definition:

The asexual form of a fungus which reproduces by releasing spores which are genetically identical to each other and to the parent.

463. anaphase
Definition:

The stage in mitosis following metaphase. The paired chromatids are separated from each other and moved to opposite ends of the cell. The stage begins as soon as the centromeres connecting each chromatid to its pair break and ends when the two new sets of chromosomes arrive at opposite ends of the cell.

464. anaphase I
Definition:

The stage in the first meiotic division of meiosis that follows metaphase I. The pairs of homologous chromosomes are separated from each other and moved to opposite ends of the cell. This stage begins as soon as homologous chromosomes begin separating and ends when the chromosomes arrive at opposite ends of the cell.

465. anaphase II
Definition:

The stage in the second meiotic division of meiosis that follows metaphase II. In each cell produced during the first meiotic division, the paired chromatids are separated from each other and moved to opposite ends of the cell. The stage begins as soon as the centromeres connecting each chromatid to its pair break and ends when the two new sets of chromosomes arrive at opposite ends of each cell.

466. anaphrodisiac
Definition:

A chemical that inhibits sexual response.

467. anaphylactic shock (anaphylaxis, type I reaction)
Definition:

A potentially fatal form of shock brought on by an extreme allergic reaction or immune response; symptoms include a sudden drop in blood pressure, difficulty in breathing, reduced body temperature, and nausea.

468. anaphylactogenesis
Definition:

The process of causing or creating anaphylactic shock.

469. anaphylactoid
Author: PharmInfoNet
Definition:

Resembling anaphylaxis, an immediate, transient allergic reaction.

470. anaphylatoxins
Author: Mirrored from Tsute Chen's Glossary of Microbiology
Definition:

The C3a and C5a fractions during complement fixation. They act to mimic some of the reactions of anaphylaxis and can induce the release of histamine from mast cells. C5a is also chemotactic for neutrophils and monocytes.

471. anaphylotoxin (anaphylatoxin)
Definition:

A substance which stimulates the release of histamines (which causes tissue inflammation) as part of an immunological response toward a foreign antigen.This can lead to anaphylactic shock.

472. anaplasia (anaplastia; adj. anaplastic)
Definition:

1. The loss of cellular organization and differentiation; typical of a tumor.
2. A phase in the evolutionary development of a species characterized by increase hardiness and diversification.

473. anaplastic
Definition:

Relating to anaplasia or anaplasty.

474. anaplasty
Definition:

The surgical repair or replacement of damaged organs, tissue, or body parts.

475. anaplerosis
Definition:

1. The surgical replacement of damaged or defective body parts.
2. An intermediate enzyme reaction that replaces the concentration of vital reacting compound that has been depleted in an organism.

476. anaplerotic reaction
Definition:

An enzyme-catalyzed chemical reaction that recharges the supply of intermediate molecules in various metabolic reactions such as the citric acid cycle.

477. anaptic
Definition:

Suffering from an impaired sense of touch.

478. anatomy
Definition:

The study of the structure of the body and the relationship between its parts.

479. anatropous
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

Of an ovule, inverted so that the micropyle faces the placenta.

480. anchor ice
Author:
Definition:

Ice formed below the surface of a stream, on the stream bed, or upon a submerged body or structure.

481. anchorage dependence
Definition:

The phenomena that many mammalian cells won't culture properly unless they're grown in single layers of cells anchored to glass or plastic substrates. This makes it difficult to culture such cells on a large scale. Only transformed cells, hybridomas and hematopoietic cells are easily grown in suspension cultures, which are preferred because they're easier to maintain.

482. Andersen sampler
Definition:

A device that collects microscopic plants from the air by a series of filters which eventually deposit the collected matter onto agar plates.

483. androdioecious
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

Having bisexual flowers and male flowers, on separate plants.

484. androecium
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

The stamens of one flower collectively.

485. androgenetic merogony
Definition:

The development of an egg fragment that has been fertilized by sperm but has no nuclei from the egg.

486. androgens
Definition:

A class of male hormones (which includes testosterone and androsterone) that is responsible for the development of male secondary characteristics (deep voice, facial hair, etc.).

487. androgynal
Author: Mirrored from Dave Sutton's Aquatic Plant Glossary
Definition:

Bearing staminate and pistillate flowers on the same parent stem.

488. androgynophore
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

A stalk bearing both the androecium and gynoecium of a flower above the level of insertion of the perianth.

489. androgynous
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

In botany: having male and female flowers in the same inflorescence. In general: having characteristics of both sexes.

490. andrologist
Author: Fertilitext
Definition:

A medical specialist who treats sperm problems.

491. andromonoecious
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

Having bisexual and male flowers on the same plant.

492. andropathy
Definition:

Any disease or condition that affects only males.

493. androphore
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

A stalk bearing the androecium.

494. androsterone
Definition:

A male sex hormone, derived from progesterone, which is seven times weaker than testosterone. It is found in the plasma and urine of both men and women. Formula: C₁₉H₃₀O₂.

495. anemia (adj.: anemic)
Definition:

A condition where there is a lower than normal amount of hemoglobin in the blood and red blood cell production is reduced. Often causes pallor and fatigue.

496. anemophilous
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

Pollinated by wind.

497. anemophily
Author: Mirrored from Dave Sutton's Aquatic Plant Glossary
Definition:

Pollination by wind.

498. anencephaly
Definition:

A condition where the brain fails to develop and may be only partially present or completely absent.

499. anergize
Definition:

To cause an organism to become unable to respond to an antigen (such as invading foreign particles) or to an antibody.

500. anergy
Definition:

1. immunology - The failure of an organism's immune system to respond to an antigen or an antibody.
2. medicine - An aberrant shortage of energy.

501. anesthesia
Definition:

1. Loss of normal sensation or feeling.
   
2. A drug used to produce anesthesia.

502. anesthesiology (anesthesiologist)
Definition:

The medical study of how to eliminate pain and sensation in people undergoing surgery and other medical procedures. An anesthesiologist is a doctor administers anaesthesia during surgery.

503. aneuploid (aneuploidy)
Definition:

Describes a cell or organism which has an abnormal total number of chromosomes and where numbers of individual chromosomes are out of proportion with the numbers of the other chromosomes. Too many chromosomes is called hyperploidy; too few is called hypoploidy. Aneuploidy is the opposite of euploidy.

504. angina
Definition:

1. A type of chest pain which feels like the chest is being constricted and/or a feeling of being suffocated. This occurs when the heart is not getting enough oxygen such as during stress, excitement, or physical exertion.
2. Any type of spasmodic, constricting, or choking pain can be called angina.
3. A throat inflammation.

505. angina (angina pectoris)
Author: Guo Li
Definition:

This is the term used by many people when they are referring to a discomfort of cardiac origins. There are several types of angina and not all originated from the heart. Angina pectoris is the sensation of chest pain, usually brought on by physically or emotionally stressful situations. Angina is usually due to atherosclerotic heart disease which is related to blood cholesterol levels. Coronary vasospasm in an apparently normal vessel can also cause angina. A patient with angina may show abnormal tracings of EKG and may progress to have a heart attack .

506. angioblast
Definition:

1. A cell in the embryo which develops into blood vessel tissue.
2. An embryonic mesenchymal tissue which differentiates into the blood cells and blood vessels.

507. angiogenesis
Definition:

The formation of new blood vessels. This occurs normally during the development of the embryo, but can also occur abnormally around malignant tumors.

508. angiogram
Author: Guo Li
Definition:

This is an x-ray procedure to study the patency and flow of blood in blood vessels.

509. angiography
Definition:

This is a technique of viewing blood vessels by injecting them with a radio-opaque dye and then x-raying them.

510. angioma (pl. angiomata)
Definition:

This is a swelling caused by expanded blood vessels.

511. angiopathy (macroangiopathy, microangiopathy)
Author: PharmInfoNet
Definition:

Disease of the blood vessels (arteries, veins, and capillaries) that occurs when someone has diabetes for a long time. There are two types of angiopathy: macroangiopathy and microangiopathy. In macroangiopathy, fat and blood clots build up in the large blood vessels, stick to the vessel walls, and block the flow of blood. In microangiopathy, the walls of the smaller blood vessels become so thick and weak that they bleed, leak protein, and slow the flow of blood through the body. Then the cells, for example, the ones in the center of the eye, do not get enough blood and may be damaged.

512. angiosperm
Definition:

A flowering, fruit-bearing plant or tree; the ovules (and therefore seeds) of these plants develop within an enclosed ovary.

513. Angiospermae
Author: Mirrored from Dave Sutton's Aquatic Plant Glossary
Definition:

A major division of the plant kingdom, commonly called flowering plants as their reproductive organs are in flowers, having seeds which develop in a closed ovary made of carpels, a very reduced gametophyte, and endosperm develop from a triple fusion nucleus.

514. angle of repose
Author:
Definition:

The maximum angle of slope (measured from horizontal plane) at which loose, cohesionless material will come to rest on a pile of similar material.

515. angle-closure glaucoma
Author: Guo Li
Definition:

Angle-closure glaucoma affects patients have shallow anterior eye chambers; the outflow of aqueous fluid at the angle of the anterior chamber is obstructed. This condition ften affects women between 40 to 60 years of age.

516. angustiseptate
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

In botany terminology, describes a plant part which has narrow partitions. Compare latiseptate.

517. anhydride
Definition:

A compound that becomes an acid in the presence of water or becomes a base when water is removed.

518. anicteric
Definition:

An anicteric malfunction of the liver is one which does not have to do with jaundice.

519. animal cell culture
Definition:

Mammalian cells are fragile and harder to grow than other cell types, but their large-scale culturing is an economic boon because it allows for the production of proteins that are otherwise difficult/expensive/unethical to extract from living organisms. There are two basic ways of culturing animal cells:
• The cells are immobilized on a substrate and then perfused with culture medium;
• The cells are in a free suspension which is very gently mixed and aerated.

520. anion (adj. anionic)
Definition:

A negatively-charged ion.

521. anion exchange resin
Definition:

A resin with fixed cationic groups which is used in chromatography to separate anionic molecules.

522. anionic detergent
Definition:

A detergent, often an alkyl sulfonate or alkaryl sulfonate, which has a negatively charged functional group.

523. anisogamy
Definition:

A condition where the gametes of a species have different sizes. In general, the smaller, more mobile gamete is "male" and the larger one which is packed with food and other things to give the potential zygote a good start (and is less mobile as a result) is the "female." The principle behind anisogamy is a division of the labor necessary for two gametes to unite and successfully develop.

524. anisometropia
Author: Guo Li
Definition:

This is a difference in the refractive errors of the two eyes.

525. anisotropic
Definition:

Describes a structure whose appearance varies with the angle of observation.

526. anisotropic membrane
Definition:

This type of synthetic membrane has an asymmetric pore structure: a thin film with tight pores backed by a thicker film with wider pores. This type of membrane is used for ultrafiltration and reverse osmosis; the porous side faces the feed stream and the tight-pored side faces the product stream.

527. ankylosing spondilitis
Definition:

A form of rheumatoid arthritis of the spine which is characterized by progressive, painful stiffening of the joints and ligaments. It almost exclusively afflicts young men.

528. anneal
Definition:

1. The sustained heating of a material such as steel or glass at a specific high temperature, followed by gradual cooling; this is done to eliminate weakness or to produce other qualities.
2. The pairing of complementary DNA or RNA sequences, via hydrogen bonding, to form a double-stranded molecule. Most often used to describe the binding of a short primer or probe.

529. annelid
Definition:

A worm, such as a leech or earthworm, belonging to the phylum Annelida.

530. Annelida
Definition:

A phylum of metameric coelomate worms (such as earthworm and leeches) which have closed vascular systems, cuticles, and hemoglobin in the blood.

531. annual
Definition:

1. Describes a plant or other organism that completes its whole life cycle in one year
2. Occuring yearly.

532. annulus
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

A ring; in ferns, the elastic ring of cells, forming part of the sporangium wall, that initiates dehiscence.

533. annulus
Author:
Definition:

In fisheries terminology, a yearly mark formed on the hard parts (scales, bones, otoliths) of fish, corresponding to a period of slow growth.

534. anodyne
Definition:

An externally-applied salve or medication that relieves pain or discomfort.

535. anomer (adj. anomeric)
Definition:

Stereoisomers of a sugar which differ only in how they are configured about their respective carbonyl (anomeric) carbon atom.

536. anorexia
Definition:

Loss of appetite.

537. anorexia nervosa
Definition:

Anorexia nervosa is an eating disorder in which the afflicted individual avoids eating or eats extremely little out of an irrational fear of becoming or being fat. This fear/perception of being fat does not diminish as the individual loses weight (often to a dangerous extent -- some individuals may lose up to 25% of their original weight). This condition is most common among young women (ages 12 to 21) but is also found in men (particularly athletes, dancers, etc.) and in older women.

538. anorexiant
Author: PharmInfoNet
Definition:

A drug or substance that leads to anorexia or diminished appetite; appetite suppressant.

539. anorexic (anorectic)
Definition:

Lacking normal appetite.

540. anovulation
Author: Fertilitext
Definition:

The absence of ovulation.

541. anoxemia (adj.: anoxemic)
Definition:

A condition in which the blood does not carry enough oxygen to keep an organism alive.

542. anoxic culture
Definition:

A culture of anaerobic microbes which use inorganic substances other than oxygen as their terminal electron acceptors.

543. anoxic reactor
Definition:

A bioreactor which is used to treat wastewater that utterly lacks dissolved oxygen; in it, faculatively anaerobic microbes are able to oxidize the sewage because they use nitrate ions as their oxygen source.

544. anoxygenic photosynthesis
Author: Mirrored from Tsute Chen's Glossary of Microbiology
Definition:

A type of photosynthesis in green and purple bacteria in which oxygen is not produced. Use of light energy to synthesize ATP by cyclic photophosphorylation without oxygen production in green and purple bacteria.

545. antagonism (antagonist)
Definition:

An interaction between chemicals in which one partially or completely inhibits the effect of the other (e.g., a drug that blocks a hormone's receptor site would be a hormone antagonist).

546. antagonistic effect
Definition:

This is the consequence of one chemical (or group of chemicals) counteracting the effects of another chemical; the opposing chemicals cancel out each other's effects.

547. antelope
Definition:

Any of several ruminants of the family Bovidae, found in Asia and Africa. Also applied to herd animals of North America, which are similarly lean and swift-moving.

548. antennapedia complex
Definition:

A set of mutations that cause developmental defects in the limbs and appendages of the fruit fly Drosophila melanogaster, such as the development of legs ("-pedia") in the places where antennae are supposed to be.

549. anterior
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

Of floral organs, on the side of the flower farthest from the axis. Compare posterior.

550. anthelminthic (antihelminthic, helminthogogue)
Definition:

Describes a compound that kills or expells parasitic intestinal worms (helminths).

551. anther
Definition:

The pollen-producing producing part of a flower.

552. anther culture
Definition:

A plant culturing technique in which immature pollen is made to divide and grow into tissue (either callus or embryonic tissue) in either a liquid medium or on solid media. Pollen-containing anthers are removed from a flower and put in a culture medium; some microspheres survive and develop into tissue. If embryonic tissue develops, it's put in a medium favorable for shoot and root development; if it's callus tissue, it's put in a solution of hormones that will spur it to differentiate and develop shoot and root tissue.

553. antheridium
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

The fertile organ of a male gametophyte or the male organ of a bisexual gametophyte, in which male gametes are formed.

554. anthesis
Definition:

The time or action of a flower opening.

555. anthesis
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

The time of a flower's opening.

556. anthocarp
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

A false fruit consisting of the true fruit and the base of the perianth.

557. anthocyanin (pl. anthocyanins)
Definition:

A blue, purple or red, accessory pigment found in plants. Anthocyanins are water-soluble glucosides. Compare carotenoid.

558. anthracosis
Definition:

This is a lung disease that causes inflammation and fibrosis of the lung; it is caused by inhaling carbon (usually coal) dust.

559. anthrax
Author: Guo Li
Definition:

Anthrax is an infection by the gram-positive spore-forming aerobic rod-shaped bacterium, Bacillus anthracis. It usually affects sheep, cattle, horses, goats, and swine. It may infect humans, causing meningitis and pneumonia with a high rate of death.

560. anthrax (woolsorter's disease, Bacillus anthracis)
Definition:

A highly contagious and often lethal bacterial disease that is caused by Bacillus anthracis. It afflicts cattle and sheep and can be transmitted to humans via infected raw meat, blood, or other fluids. Anthrax causes high fever, convulsions, and lung lesions.

561. anthropoid
Definition:

This refers to the higher primates (humans, apes, and monkeys). The word is derived from the Greek word anthropos, which means "man" or "human".

562. anthropomorphism
Definition:

The application of human qualities to inanimate objects, animals and other life forms, and natural phenomena, such as to cars or hurricanes.

563. anti-idiotype antibody
Definition:

Any of several antibodies that are produced against the unique amino acid sequence that makes up the antigen binding site in the variable region of an antibody. Anti-idiotype antibodies can be used as vaccines.

564. anti-inflammatory
Definition:

A compound that reduces inflammation.

565. anti-metabolite
Author: Mirrored from Tsute Chen's Glossary of Microbiology
Definition:

An analog of the end-product of a metabolic pathway that causes feedback inhibition or repression, but cannot replace the genuine product; used for selecting feedback-deficient mutants.

566. anti-native DNA antibody
Author: Guo Li
Definition:

This is an antibody found only in the blood of patients with lupus. (Some patients with lupus may test negative for this antibody, though).

567. anti-nuclear antibody
Author: Mirrored from Tsute Chen's Glossary of Microbiology
Definition:

Anti-nuclear antibody (ANA) is an antibody against nuclear materials such as DNA, RNA, histone or non-histone proteins. ANA is usually found in the serum of individuals with certain autoimmune diseases, e.g., systemic lupus erythematosus (SLE), Sjogren's syndrome, polymyositis, systemic sclerosis, etc. Different diseases have ANA against different nuclear components.

568. anti-phospholipid syndrome
Author: Guo Li
Definition:

Anti-phospholipid syndrome is an autosomally inherited genetic disorder in which an affected individual produces antibodies against his/her own cellular phospholipid components. This is manifested clinically as a tendency to have arterial and venous thrombosis, thrombocytopenia and recurrent fetal loss (miscarriage).

569. antiandrogen
Definition:

A substance which interferes with the function of an androgen, or male sex hormone, by taking over the androgen's receptors.

570. antibiogram
Definition:

The sensitivity pattern of a given bacterial or fungal strain to a specific antibiotic.

571. antibiosis
Definition:

A relationship between two species in which one species is actively harmed (as by the production of toxins by the harming species). Compare symbiosis.

572. antibiotic
Definition:

A substance such as penicillin or tetracycline that is able to kill or inhibit the growth of certain microorganisms.

573. antibiotic assay
Definition:

A test to determine how sensitive a bacterial or fungal strain is to a range of antibiotics by measuring the microbes' ability to grow in a standard dilution of each chemical.

574. antibiotic resistance
Definition:

The ability of a bacterium to synthesize a protein that neutralizes an antibiotic.

575. antibiotic resistance genes
Definition:

Genes in a microorganism which confer resistance to antibiotics, for example by coding for enzymes which destroy it, by coding for surface proteins which prevent it from entering the microorganism, or by being a mutant form of the antibiotic's target so that it can ignore it.

576. antibody
Definition:

A protein that is produced in response to an antigen (often a virus or bacterium). It is able to combine with and neutralize the antigen.

577. antibody technology
Definition:

Techniques for the synthesis of polyclonal and monoclonal antibodies for use in research, diagnostics and therapeutics.

578. antibody-forming cells
Definition:

B cells (plasma cells) that are dedicated to producing secreted antibodies.

579. anticholinergenic (anticholinergic, parasympatholytic)
Definition:

Refers to an agent that inhibits parasympathetic neural activity by blocking the neurotransmitter acetylcholine.

580. anticholinesterase
Definition:

An agent, such as nerve gas, that blocks nerve impulses by inhibiting the activity of the enzyme cholinesterase.

581. anticipatory control
Definition:

The regulation of a system or process based on anticipated events; this is a feed-forward rather than a feedback system.

582. anticoagulant
Definition:

A compound that inhibits the clotting of blood.

583. anticodon
Definition:

A specific sequence of three nucleotides in transfer RNA which are complimentary to a codon for a specific amino acid in a messenger RNA.

584. antidepressant
Author: Guo Li
Definition:

This is a drug used to treat depression.

585. antidiabetic agent
Author: PharmInfoNet
Definition:

A substance that helps a person with diabetes control the level of glucose (sugar) in the blood so that the body works as it should. See: insulin.

586. antidiuretic
Definition:

A drug that reduces or stops the formation of urine.

587. antidyspeptic
Definition:

A compound that relieves indigestion.

588. antiemetic
Definition:

A compound that relieves nausea and vomiting.

589. antienzyme
Definition:

A protein or polypeptide that inhibits or destroys and enzyme.

590. antifoam agent
Definition:

A chemical that reduces the surface tension of foams that form on the surface of broths in fermentors because of aeration or agitation. Stearyl decanol, octal decanol, vegetable oils, silicones, sulfonates, and polypropylene glycol are typically used, though they can cause problems in refining the broth later on.

591. antifreeze protein
Definition:

This is a protein found in the extracellular fluid of some fish that live in very cold water; it inhibits the formation of ice crystals.

592. antifungicide
Definition:

A substance which kills fungi.

593. antigen
Definition:

A substance (e.g. a virus or bacterium) that causes an immune system response.

594. antigen processing / presenting cell
Definition:

A type of cell which provokes an immune response from T lymphocytes by binding foreign antigens to their surfaces and then interacting with the T cells.

595. antigenic determinant
Definition:

A molecule (such as a glycoprotein) on the surface of a microbe or macromolecule that triggers an immune response.

596. antigenic drift
Author: Mirrored from Tsute Chen's Glossary of Microbiology
Definition:

In influenza virus, minor changes in viral proteins (antigens) due to gene mutation.

597. antigenic switching
Definition:

The process by which a pathogenic microbe's genetic structure is altered to change its surface antigens in order to avoid being detected by the host's immune system.

598. antigenic variation
Definition:

A change in the structure of an antigen on the surface of a disease-causing microorganism or virus (a pathogen) so that the host's immune system no longer recognizes the pathogen and must make new antibodies to recognize the changed antigens before the host can continue to combat the disease. As a result, the host cannot stay immune to the disease.

599. antigenicity
Definition:

The ability of a substance to trigger an immune response in a particular organism.

600. antihemorrhagic
Definition:

A compound that slows or stops excessive, uncontrolled bleeding.

601. antihistamine
Definition:

A drug that relieves allergy symptoms by blocking the production or effects of histamines in the inflammatory process.

602. antihypertensive
Definition:

A compound that lowers high blood pressure.

603. antihypertensive
Author: Guo Li
Definition:

This is a drug to treat high blood pressure.

604. antimicrobial
Author: Mirrored from Tsute Chen's Glossary of Microbiology
Definition:

Harmful to microorganisms (fungi, bacteria, etc.) by either killing them or inhibiting their growth.

605. antimycin A
Definition:

This antibiotic is used to kill fungi, insects and mites; it works by blocking mitochondrial respiration by interrupting the electron transport chain in those organelles.

606. antimycotic
Definition:

An agent that kills or destroys fungi.

607. antineoplastic drug
Definition:

A drug that stops or slows the maturation and spread of tumor cells (benign or malignant).

608. antinuclear antibody
Author: Guo Li
Definition:

This is an antibody found in the blood of virtually all patients with lupus . (but patients with other problems, like rheumatoid arthritis may be positive for this test).

Normal range: no ANA present up to 1/32 dilution.

609. antioncogene (tumor-suppressor gene)
Definition:

A gene which suppresses the formation of tumors. Deletion or inactivation of this gene is believed to be a necessary prerequisite for tumor development.

610. antioxidant
Definition:

Any of many chemicals that reduce or prevent oxidation, especially within tissues. Vitamin C is a common antioxidant.

611. antiparallel
Definition:

Refers to two linear polymers that are opposite in orientation or polarity.

612. antiparasite
Definition:

A substance or chemical which kills parasites.

613. antipetalous
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

Inserted in front of the petals; opposite the petals.

614. antiport
Definition:

The cotransport of two molecules across a membrane in opposite directions.

615. antipruritic
Author: Guo Li
Definition:

Pertaining to the treatment of itching, or of a medication used to treat itching.

616. antipyretic
Definition:

A compound that reduces fever.

617. antipyretic
Author: Guo Li
Definition:

This is a drug to treat fever. Common antipyretics are acetylsalicylic acid (aspirin) and acetaminophen (Tylenol).

618. antisense RNA (anti-sense RNA)
Definition:

A complementary RNA sequence that binds to (and thus blocks the transcription of) a naturally-occuring (sense) messenger RNA molecule.

619. antisense strand (anticoding strand)
Definition:

The strand of DNA which is not used during transcription to make mRNA. The mRNA made during transcription thus has the same sequence as this strand (so that the eventual protein will be a sense version). See also sense strand.

620. antisepalous
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

Inserted in front of the sepals; opposite the sepals.

621. antiseptic
Definition:

1. A compound that prevents infection or decay by killing a wide range of pathogenic microbes.
2. The condition of being free of pathogenic microbes.

622. antiserum
Definition:

A serum containing antibodies that will work against specific viruses, bacteria, or other antigens.

623. antispasmodic
Definition:

A compound that relieves muscular spasms.

624. antispasmodic
Author: Guo Li
Definition:

This is a drug to relieve muscle spasms.

625. antisperm antibodies
Definition:

Antibodies that can attack sperm and inhibit their movement or block fertilization of the egg.

626. antitermination factor
Definition:

A gene regulatory protein that blocks signals for the transcription process to stop as a form of regulatory control over whatever the gene being transcribed is coding for.

627. antitoxin
Author: Mirrored from Tsute Chen's Glossary of Microbiology
Definition:

An antibody that specifically interacts with and neutralizes a toxin.

628. antitrypsin (alpha-1-antitrypsin, alpha-1-protease inhibitor)
Definition:

This is a glycoprotein produced in the liver which is the major antiprotease in the blood, serving mainly to inhibit leukocyte elastase. It is a single-chain molecule, has 394 amino acids and a molecular weight of 51,000.

Hereditary antitrypsin deficiency is one of the most common genetic disorders among males of European descent. Alpha-1-antitrypsin deficiency results in leukocyte elastase building up and breaking down the lining of the lung, which results in a severe form of emphysema (oxidizing agents in cigarette smoke are also known to inactivate antitrypsin, thus causing the high rates of emphysema among long-term smokers). Because over 20,000 people are affected by this deficiency, large amounts of this antiprotease are needed. To meet the demand, researchers are genetically engineering sheep that produce the antiprotease in their milk.

629. antitussive
Definition:

A compound that prevents or controls coughs.

630. antiuric
Definition:

A compound that reduces the acidity of urine.

631. antrorse
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

Directed forwards or upwards. Compare retrorse.

632. aorta
Definition:

The main artery which leaves the heart.

633. aorta
Author: Guo Li
Definition:

This is the artery arising from the left ventricle of the heart, in which blood flows from the heart to the body. The most common medical problem of the aorta is atherosclerosis.

634. aortic arch
Definition:

The part of the aorta between the ascending and descending portions which supplies blood flow to the arms, head and neck through the carotid and subclavian arteries.

635. apathy
Author: The Alzheimer's Association
Definition:

Indifference, lethargy, or general lack of emotion or feeling.

636. aperitive
Definition:

A compound (such as tetrahydrocannibanol) that stimulates the appetite.

637. apetalous
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

Without petals.

638. APGAR score
Author: Guo Li
Definition:

This is a scoring system for the evaluation of newborn babies developed by Dr. Virginia Apgar in 1953. A score of 0, 1, or 2 is given to five vital signs which are assessed at 1 minute, 5 minutes, and 10 minutes. The five vital signs are : appearance, pulse, reflex, muscle tone, and breathing pattern. The following is how the scores are given:

Score	Color	Heart Rate	Reflex	Muscle Tone/Activity	Respiration
0	blue, pale	absent	no response	limp	absent
1	body pink, extremeties blue	below 100	grimace	some flexion of extremeties	slow, irregular
2	completely pink	over 100	cough, sneeze, cry	active	good, crying

It is fair to say that APGAR score at 1 minute after birth reflects the neonate's need for attention. A low 1 minute score is not necessarily indicative of any long term problems of the baby (a normal premature child would have a low score, as might the baby of a woman under heavy analgesia). The five minutes score is a reflection of the success of effectiveness of the resuscitation. Neither are the 1 minute or 5 minute scores good indicators of future problems or performances of the child. A low Apgar score at 10 minutes and after may indicate problems, such as cerebral palsy, especially if other clinical signs are present (e.g. hypotonia, seizures, metabolic acidosis)

639. aphakia
Definition:

The loss or absence of the lens of an eye.

640. aphasia
Author: Guo Li
Definition:

This is the inability to speak or write.

641. apical
Definition:

Relating to or located at the tip (an apex).

642. apical dominance
Definition:

A situation in which the presence of a terminal bud on a branch suppresses axillary bud growth.

643. apiculate
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

Terminating in a short, sharp, flexible point.

644. apiculum
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

A short, abrupt, flexible point; adj. apiculate.

645. aplasia (adj. aplastic)
Definition:

A medical term meaning the failure to develop.

646. apocarpous
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

Of a gynoecium: consisting of two or more carpels which are free from one another or almost so.

647. apoenzyme (apoferment)
Definition:

The inactive protein part of an enzyme; it doesn't include any non-protein cofactors or side groups that might be needed for the enzyme to engage in catalytic activity.

648. apolipoprotein
Definition:

The protein component of a lipoprotein

649. apomict
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

A plant that produces viable seed without fertilization.

650. apomixis
Author: Mirrored from Dave Sutton's Aquatic Plant Glossary
Definition:

In general, reproducing without sexual reproduction; often used to denote seed production without a sexual process having been involved.

651. aponeurosis (adj.: aponeurotic)
Definition:

A type of connective tissue which attaches muscle to other tissue types, including bone. Appears as flat, fibrous sheets.

652. apoptosis (programmed cell death)
Author: Douglas Miles
Definition:

Programed cell death as signalled by the nuclei in normally functioning human and animal cells when age or state of cell health and condition dictates. Cancerous cells, however, are unable to experience the normal cell transduction or apoptosis-driven natural cell death process.

653. apparent viscosity
Definition:

This refers to the ratio of shear stress to shear rate in a fluid; this ratio is dependent on the rate of shear.

654. appendage
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

A structure arising from the surface or extending beyond the tip of another structure.

655. appendectomy (appendicitis)
Author: Guo Li
Definition:

This is surgery to remove the appendix because of confirmed or suspected infection of the appendix (appendicitis). In the procedure, an incision about 5 centimeters long is made in the right lower abdomen. The intestine is examined and the appendix is found. Even if the appendix is not inflamed, it will be removed, unless there is some reason not to do so. The abdominal wall is then closed by suturing together the layers.

If there is some reason that surgical removal of the appendix is not possible (e.g. lack of proper facilities), the patient is put on antibiotics and everyone waits for either the appendicitis to subside or for surgery to become possible.

The surgery carries with it anesthesia risks as well as the risk of infection and bleeding.

The consequences of not having the treatment include rupture (perforation) of the appendix, which can lead to infection of the inside lining of the abdominal wall (peritonitis). Peritonitis not only increases the length of hospital stay and need for further treatment, but also increases the chance of wide-spread bacterial infection (sepsis), which can be fatal.

656. appendicitis
Author: Guo Li
Definition:

This is the inflammation of the appendix. Early pain is around the umbilicus (belly button), later pain is localized in the right lower quadrant of the abdomen; the associated symptoms are nausea and vomiting. Diagnosis is based on the clinical progress, examination and laboratory findings of elevated white blood cells. Once diagnosed and if facility is available, appendectomy is suggested.

657. appendix
Author: Guo Li
Definition:

The vermiform appendix (as opposed to other types of appendices) is an attachment of 8 to 13 cm, rich in lymphoid tissue, to the caecum.

658. appressed
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

Pressed closely against but not united with.

659. approriate technology
Definition:

This refers to the use of equipment and scientific techniques that are specifically suited to local conditions and available resources, particularly in undeveloped or developing areas.

660. apraxia
Definition:

This medical term describes the condition of not being able to perform coordinated motor activities (it specifically refers to the inability to use an object correctly) when the person is not suffering from paralysis or damage to muscles, bone, or sensory organs.

661. aprotic
Definition:

This refers to an atom or molecule that will neither donate nor accept protons.

662. aprotinin
Definition:

A protein found in the blood and body tissues which neutralizes enzymes such as chymotrypsin, kallikrein, papain, plasmin and trypsin.

663. aptamer (adaptamer)
Definition:

A type of synthetic oligonucleotide that can bind to a particular target molecule, such as a protein or metabolite.

664. APUD cells
Definition:

"Amine Precursor Uptake and Decarboxylation": a group of apparently unrelated endocrine cells found throughout the body which have a number of similar characteristics and which make a number of hormones with similar structures (including serotonin, epinephrine, dopamine, neurotensin, and norepinephrine).

665. apudoma
Definition:

A tumor composed of APUD cells and which secretes one or more hormones or amines.

666. apurinic DNA
Definition:

A DNA molecule that has lost adenine and guanine, its purine bases. Apurinic DNA can be produced by treating the DNA with acid.

667. apurinic site
Definition:

A site on DNA where a base is missing, in this case a purine (either adenine or guanine), but the phosphodiester backbone of the DNA is still intact. Compare with apyrimidinic site.

668. apyrimidinic site
Definition:

A site on DNA where a base is missing, in this case a pyrimidine (either cytosine or thymine), but the phosphodiester backbone is still intact. Compare with apurinic site.

669. aquaculture (aquiculture)
Definition:

The cultivation of aquatic plants and animals for food or other purposes; this term often refers specifically to freshwater cultivation, as opposed to marine cultivation (mariculture).

670. aqualfs
Author:
Definition:

Soils with an aquic or peraquic moisture regime and having clay accumulating in the B-horizon; wet alfisols.

671. aquatic
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

Living in or on water for all or a substantial part of the life span (generally restricted to fresh/inland waters).

672. aquatic plants
Author: Mirrored from Dave Sutton's Aquatic Plant Glossary
Definition:

Plants that must grow in water whether rooted in the mud or floating without anchorage; plants that must complete part or all of their life cycle in or near the water.

673. aquatic roots
Author:
Definition:

Roots that develop on stems above the normal position occupied by roots, in response to prolonged inundation with water.

674. aquents
Author:
Definition:

Soils with an aquic or peraquic moisture regime and lacking distinct soil horizons in the subsoil; wet entisols.

675. aqueous
Definition:

A solution in which water is the solvent.

676. aqueous humor
Definition:

The clear, watery fluid inside the eyeball which helps it keep its shape.

677. aquepts
Author:
Definition:

Soils with an aquic moisture regime and showing some soil development in the B-horizon; wet inceptisols.

678. aquic moisture regime
Author:
Definition:

A moisture condition associated with a seasonal reducing environment that is virtually free of dissolved oxygen because the soil is saturated by ground water or by water of the capillary fringe as in soils in aquic suborders and aquic subgroups.

679. aquic moisture regime
Author:
Definition:

A moisture condition associated with a seasonal reducing environment that is virtually free of dissolved oxygen because the soil is saturated by ground water or by water of the capillary fringe as in soils in aquic suborders and aquic subgroups.

680. aquifer
Author:
Definition:

1. A subsurface layer of rock permeable by water. Although gravel, sand, sandstone and limestone are the best conveyers of water, the bulk of the earth's rock is composed of clay, shale and crystalline.
2. A saturated permeable material (often sand, gravel, sandstone or limestone) that contains or carries groundwater.
3. An underground, water-bearing layer of earth, porous rock, sand, or gravel, through which water can seep or be held in natural storage. Aquifers generally hold sufficient water to be used as a water supply.

681. aquods (wet spodsols)
Author:
Definition:

Soils having an accumulation of iron, aluminum and organic matter in the B-horizon in addition to having an aquic moisture regime.

682. Arabidopsis thaliana
Definition:

Arabidopsis thaliana is a small, weedy flowering plant that has been intensely studied as a model for plant biology and pathology. It has been such a favorite of researchers primarily because it grows rapidly and has a compact genome.

683. arabinose
Image: View the chemical structure
Definition:

A monosaccharide, or simple sugar, with the chemical formula C₅H₁₀O₅. This sugar is found in many plants.

684. arabinosyladenine (araA)
Definition:

An antibiotic used to treat viral encephalitis. Its structure is derived from the purine adenosine by replacing the simple sugar ribose with the simple sugar arabinose.

685. arabinosylcytosine (araC)
Definition:

An antibiotic which acts by blocking DNA synthesis. Its structure is derived from the pyrimidine cytosine by replacing the simple sugar ribose with the simple sugar arabinose.

686. arachidonate (arachidonic acid)
Definition:

An essential unsaturated fatty acid that humans use to synthesize regulatory molecules such as prostaglandins and thromboxanes. It is found in fatty animal tissue such as egg yolk and liver.

687. arachnid
Definition:

An organism of the class Arachnida in the kingdom Animalia. For example, a spider.

688. arachnobutyrophobia
Definition:

Fear of peanut butter. Really.

689. arachnodactyly
Definition:

A skeletal disorder where the patient has unusually long, thin bones, especially noticeable in the fingers and toes.

690. arachnoid
Author: Mirrored from Dave Sutton's Aquatic Plant Glossary
Definition:

Like a cobweb; covered with or consisting of soft fibers or hairs so entangled as to give a cobwebby appearance.

691. arborescent
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

Resembling a tree (applied to non-woody plants attaining tree height and to shrubs tending to become tree-like in size). Compare dendroid.

692. arbutin
Image: View the chemical structure
Definition:

A glycoside found in the bearberry and related plants which has been used to treat urinary-tract diseases.

693. Archae (Archaebacteria)
Definition:

This is a super-classification of odd bacteria that are neither prokaryotes nor eukaryotes; some scientists believe they represent a separate kingdom. The primary genus is Archaebacteria, whose members fall in three categories: microbes that can live in extremely salty environments (halophiles), microbes that produce methane (methanogens), and microbes that can live in extremely hot environments (thermophiles). All are of interest to biotechnologists because they have unique biochemical features (e.g., the enzymes of the theromophiles are extremely stable at high temperatures).

694. arched roots
Author:
Definition:

Roots produced on the plant stems in a position above the normal position of roots, which serve to brace the plant during and following periods of prolonged inundation with water.

695. archegonium
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

The structure on the pteridophyte prothallus that produces the sessile female gametes. Compare antheridium.

696. area under the curve (AUC)
Author: PharmInfoNet
Definition:

A measure of how much of a drug reaches the bloodstream in a set period of time, usually 24 hours. AUC is calculated by plotting drug blood concentration at various times during a 24-hour or longer period and then measuring the area under the curve between 0 and 24 hours as shown in the figure to the right.

697. areal cover
Author:
Definition:

A measure of dominance that defines the degree to which above ground portions of plants cover the ground surface; it is possible for the total areal cover for all strata combined in a community or for single stratum to exceed 100 percent because:
1. most plant communities consist of two or more vegetative strata;
2. areal cover is estimated by vegetative layer; and
3. foliage within a single layer may overlap.

698. areola (pl.: areolae, areolas adj.: areolar)
Definition:

1. A small space or hole in a tissue.
2. An area of tissue surrounding something which has different pigmentation than other nearby tissues. Examples include the iris around the pupil of the eye, the area around the nipple of a breast, and certain types of skin rashes.

699. areole
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

A space between the threads of a net; in the family Cactaceae, a cluster of hairs/spines/bristles borne at the node of a leafless stem; in Mimosaceae (for example), a distinct, oblong or elliptical area on the face of a seed, bounded by a fine line. adj. areolate.

700. arginine
Image: View the chemical structure
Author: Courtesy of MacMolecule
Definition:

One of the twenty naturally occurring amino acids. Has the following chemical characteristics:


pKa1   pKa2   pKa3       pI      Water Solubility (30deg C)
2.17   9.04   12.48      10.76            48 (as HCl salt)

701. aril
Definition:

A fleshy outgrowth that partially or completely surrounds the seed in some plants.

702. aristate
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

Having a stiff, bristle-like appendage or tip.

703. aristate
Author: Mirrored from Dave Sutton's Aquatic Plant Glossary
Definition:

Awned; having an awn.

704. aristulate
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

Having a small bristle-like appendage.

705. arrayed library
Definition:

Individual primary recombinant clones (hosted in phage, cosmid, YAC, or other vector) that are placed in two-dimensional arrays in microtiter dishes. Each primary clone can be identified by the identity of the plate and the clone location (row and column) on that plate. Arrayed libraries of clones can be used for many applications, including screening for a specific gene or genomic region of interest as well as for physical mapping. Information gathered on individual clones from various genetic linkage and physical map analyses is entered into a relational database and used to construct physical and genetic linkage maps simultaneously; clone identifiers serve to interrelate the multilevel maps. Compare library, genomic library.

706. Arrhenius equation
Definition:

This equation expresses the logarithmic relationship between the rate constant of a reaction and the reciprocal of the temperature (expressed in K).

707. arroyo
Author:
Definition:

1. A gully, ravine, or canyon created by a perennial or intermittent stream, with characteristic steep slopes frequently covered with vegetation.
2. Waterway of ephemeral stream deeply carved in rock or ancient alluvium.

708. arterial blood gas assay (ABG)
Author: Mirrored from Guo Li's Dictionary of On-Line Medical Resources
Definition:

This is a laboratory test of blood samples taken from an artery for pH, partial pressure of oxygen PO₂, partial pressure of carbon dioxide PCO₂, and oxygen saturation (SO₂). normal values:

pH = 7.32 to 7.45
PO₂ = 90 to 98
PCO₂ = 35 to 45
Sat O₂ = 96 to 98

709. arterial line
Author: Guo Li
Definition:

This is a catheter placed in an artery for the purpose of displaying arterial blood pressure and sampling of arterial blood. Complications of an arterial line include: bleeding, hematoma, pain, brachial, femoral or radial nerve injury.

710. arteriography
Author: Guo Li
Definition:

This is a radiological procedure to assess the patency of the arterial circulation. Radiopaque dye is injected through a thin catheter placed in the artery. X-ray of the flow pattern of the dye is taken. Abnormal findings include obstruction, occlusion, narrowing, and tumor.

711. arteriosclerosis
Author: PharmInfoNet
Definition:

A group of diseases in which the walls of the arteries get thick and hard. In one type of arteriosclerosis, fat builds up inside the walls and slows the blood flow. These diseases often occur in people who have had diabetes for a long time. See also: atherosclerosis.

712. artery
Author: PharmInfoNet
Definition:

A large blood vessel that carries blood from the heart to other parts of the body. Arteries are thicker and have walls that are stronger and more elastic than the walls of veins.

713. arthralgia
Author: PharmInfoNet
Definition:

Severe joint pain.

714. arthralgia
Author: Guo Li
Definition:

This is pain in a joint.

715. arthritis
Author: Guo Li
Definition:

Arthritis is the inflammation of a joint. Common types of arthritis are rheumatoid arthritis and osteoarthritis.

716. arthropod
Definition:

An arthropod is a member of a phylum of of invertebrate animals that includes insects, arachnids (spiders and mites), and crustaceans (crabs, lobsters, pillbugs, shrimp, etc.). They are members of the phylum Arthropoda and are characterized by having exoskeletons and jointed appendages.

This word comes from the Greek words arthron (joint) and podos (foot).

717. arthroscope
Author: Guo Li
Definition:

This is an instrument used to examine the interior of a joint.

Modern equipment for arthroscopy would have included a fiberoptic setup so that the arthroscopic views are taped with VCR and displayed on TV screen. In addition to viewing the condition of the joint, arthroscopy allows surgery to be performed for torn cartilage, torn ligament, arthritic conditions, loose fragments, and meniscal diseases.

Material effects, risks and side effects: infection of the joint; bleeding in the joint; thrombophlebitis; and anaesthesia risks.

718. arthroscopy
Author: Guo Li
Definition:

The use of an arthroscope to examine a joint.

719. arthrospore
Definition:

This is a cell formed by the fragmentation of a fungus' hyphae.

720. Arthus reaction
Definition:

An immediate inflammatory response to solid deposits of antigen-antibody complexes within tissues or blood vessels walls.

721. articulate
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

Jointed; having joints where separation may occur naturally; of a stem, having nodes.

722. articulate (articulated)
Author: Mirrored from Dave Sutton's Aquatic Plant Glossary
Definition:

Having joints; jointed; provided with places where separation may take place.

723. artifact
Definition:

The appearance of a structure under a microscope which is not actually present but is the result of procedures used to prepare the slide. An apparent experimental result that is not actually real but is due to the experimental methods.

724. artificial insemination (AI)
Definition:

The placement of a sperm sample inside the female reproductive tract to improve the female’s chances of getting pregnant. (See also intracervical insemination, intrauterine insemination, intratubal insemination).

725. artificial intelligence (AI)
Definition:

In a nutshell, artificial intellence (AI) is the study of how to create a computer that can "think" like a human being. See also expert systems and machine learning.

For more information, visit The AI-FAQs.

726. artificial life (AL, alife, a-life)
Definition:

Artificial life (AL, alife) is a scientific discipline in which researchers study life by creating computer programs that recreate biological systems from scratch.

For more information, visit Artificial Life Online.

727. artificial neural nets (ANN)
Definition:

Artificial Neural Nets (ANN) are computer models of biological nerve cell networks. For more information, visit the Neural Network FAQ.

728. artificial selection
Definition:

The selective breeding by humans towards a desired trait in a plant, animal, or other organism which is of value (usually economic) to the humans. The process operates on the same principles as natural selection.

729. artificial wetlands
Author:
Definition:

Wetlands created by the activities of man, either purposefully or accidentally.

730. asbestosis
Definition:

This is a lung disease that causes inflammation and fibrosis of the lung; it is caused by inhaling asbestos dust. This disease predisposes the sufferer to develop cancer of the lung and mesothelioma of the pleura.

731. Ascaris
Definition:

A genus of nematode worms, including the species of roundworm that can infect the intestines of humans and swine. Members of this genus resemble earthworms and have three-lipped mouths.

732. ascending
Author: Mirrored from Dave Sutton's Aquatic Plant Glossary
Definition:

Rising or curving upward.

733. ascending aorta
Definition:

The part of the aorta between the top of the left ventricle of the heart and the aortic arch. The ascending aorta supplies blood to the myocardium (middle layer of the heart wall) through the coronary arteries.

734. ascites
Definition:

1. Edema, or the abnormal buildup of fluid, in the abdominal cavity outside the intestines. This is often a symptom/complication of liver problems or cancer of abdominal organs.
2. A tumor (hybridoma) in the abdominal cavity of a genetically-engineered mouse that secretes a serum containing a desired monoclonal antibody.

735. ascitic tumor
Definition:

A tumor of the abdominal cavity which often causes edema in that cavity.

736. Ascomycotina (cup fungi, sac fungi)
Image: cup fungi, morel, powdery mildew
Definition:

A subdivision of true fungi commonly known as cup or sac fungi. They reproduce asexually through externally-produced spores called conidia and sexually with the aid of specialized sacs called asci. This division includes yeasts, morels, truffles, powdery mildews, ergot and fungi responsible for other plant diseases such as chestnut blight, peach leaf curl and Dutch elm disease.

737. asepalous
Author: Mirrored from Dave Sutton's Aquatic Plant Glossary
Definition:

Without sepals.

738. asepsis
Definition:

The condition of a substance being free of microbial contamination.

739. aseptic technique
Definition:

Procedures used by microbiologists and clinicians to keep cultures, sterile instruments and media, and people free of microbial contamination.

740. asexual
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

Not forming part of a cycle which involves fertilization and meiosis.

741. asexual reproduction
Definition:

Reproduction in which an organism produces one or more clones of itself, such as by fission or budding.

742. asparagine
Image: View the chemical structure
Author: Courtesy of MacMolecule
Definition:

One of the twenty naturally occurring amino acids. Has the following chemical characteristics:


pKa1   pKa2     pI      Water Solubility (30deg C)
2.02   8.80    5.41            3.6

743. aspartame (Nutrasweet )
Image: View the chemical structure
Definition:

An artifical sweetener (a synthetic dipeptide ester, N-L-alpha-aspartyl-L-phenylalanine methyl ester, or L-asp-L-phe-OMe) which is 200 times sweeter than table sugar (sucrose).

744. aspartate
Author: The Alzheimer's Association
Definition:

A neurotransmitter; aspartate can be an excitotoxin.

745. aspartic acid
Image: View the chemical structure
Author: Courtesy of MacMolecule
Definition:

One of the twenty naturally occurring amino acids. Has the following chemical characteristics:


pKa1   pKa2    pKa3     pI      Water Solubility (30deg C)
2.09   3.86    9.82    2.97            0.6

746. aspect (exposure)
Author:
Definition:

Direction that an area, especially a slope, faces.

747. Aspergillus
Definition:

Aspergillus is a genus of filamentous fungi belonging to Deuteromycetes. Fungi in this genus are easy to grow; some produce a wide range of useful enzymes, but others are dangerous pests and pathogens. For instance, A. niger is used to produce citric acid, gluconic acid, amylase, proteases, and peptic enzymes, but A. parasiticus grows on grains and produces aflatoxin, a powerful liver carcinogen.

748. asperulate
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

Slightly rough to the touch.

749. asphyxia
Author: Guo Li
Definition:

This is the condition of lacking oxygen or being unable to breathe.

750. asphyxiant
Definition:

A type of poison which works by depriving tissues of oxygen.

751. aspiration
Definition:

1. Withdrawal by suction.
2. Sucking foreign material into the lungs as one takes a breath.

752. assay
Definition:

A test for a particular substance.

753. association (aggregation)
Author:
Definition:

A collection of units or parts into a mass or whole; for example, a group of animals, plants or both. A statement of physical proximity or grouping, without necessarily requiring or implying interactions between units of the group, in contrast to "community", which does. Similar or equivalent to "aggregation".

754. astemizole (Astemisan, Hismanal, Histamen, Histaminos,Paralergin, Waruzol)
Definition:

This is a non-sedating drug used to treat allergies; it's a histamine H1-receptor antagonist.

755. aster
Definition:

A star-shaped structure, composed of microtubules, which surrounds the centrioles during mitosis in animals. The aster forms during prophase. The spindle fibers arise gradually between the two asters (at opposite ends of the cell) until they attach to the kinetochores of the centromeres of each chromosome. Asters are not found in vascular plant cells.

756. asthma
Author: Guo Li
Definition:

This is a respiratory disease characterized by an increased responsiveness of the trachea and bronchi to various stimuli, and manifested by widespread narrowing of the airways that changes in severity either spontaneously or as a result of treatment.

Symptoms: recurrent attacks of wheezing, shortness of breath, cough, and a feeling of tightness in the chest.

757. astrobiology (exobiology)
Definition:

The study of life that potentially exists on planets or celestial bodies other than Earth.

758. astroblast
Definition:

A cell that turns into an astrocyte.

759. astroblastoma
Definition:

A rare form of cancer characterized by tumors made up of large cells with two or three nuclei.

760. astrocyte (astroglia)
Definition:

A star-shaped cell of the nervous system which provides nutrients, support and insulation for neurons.

761. astrocytoma
Definition:

A tumor composed of astrocytes.

762. astrocytosis (astrogliosis)
Definition:

An abnormal increase in the number of astrocytes due to the destruction of nearby neurons, typically because of hypoglycemia or oxygen deprivation.

763. asymptomatic
Author: PharmInfoNet
Definition:

No symptoms; no clear sign of disease present.

764. AT content
Definition:

The percentage of nitrogenous bases on a DNA molecule which are either adenine or thymine (from a possibility of four different ones, also including cytosine and guanine).

Also see GC content.

765. AT/GC ratio
Definition:

The ratio of adenine-thymine base pairs to guanine-cytosine base pairs on a DNA molecule.

766. atactic
Definition:

This describes a polymer that has no regularly repeated structural units.

767. ataxia
Definition:

This is a condition in which a person is not able to coordinate his or her muscle movements; as a result, he or she cannot walk or move properly.

768. atelectasis
Author: Guo Li
Definition:

This is the collapse of the small airways of the lung, as seen in chest X-rays.

769. atherogenic
Author: PharmInfoNet
Definition:

Having the capacity to start or accelerate the process of atherogenesis (the formation of lipid deposits in the arteries).

770. atherosclerosis
Author: PharmInfoNet
Definition:

One of many diseases in which fat builds up in the large- and medium-sized arteries. This buildup of fat may slow down or stop blood flow. This disease can happen to people who have had diabetes for a long time.

771. atmosphere
Definition:

1. The mixture of gases surrounding the Earth and other planets.
2. A unit of pressure which equals 101.325 kPa.

772. atom
Definition:

This is the tiniest particle of matter that retains the chemical properties of an element; atoms are typically composed of neutral subatomic particles (neutrons), positively-charged particles (protons) and negatively-charged particles (electrons).

773. atomic mass (atomic weight)
Definition:

This is the average mass of the naturally occurring isotopes of an element; the value takes into account the different natural abundances of the isotopes. The value is expressed relative to the value of exactly 12 for carbon-12

774. atomic number
Definition:

This is the number of protons in the nucleus of an atom; it is used to define the position of an element in the periodic table.

775. atomic weight
Author: Mirrored from Tsute Chen's Glossary of Microbiology
Definition:

The average weight of an atom of an element, i.e. the total mass of protons and neutrons in an atom.

776. atopic dermatitis
Author: Guo Li
Definition:

This type of skin irritation is often found in infants, involving face, elbow and knee flexures; it tends to go into remission with age.

777. atopy
Author: PharmInfoNet
Definition:

An allergic reaction with strong family tendencies.

778. ATP synthase
Definition:

An enzyme that catalyzes the conversion of phosphate and ADP into ATP during oxidative phosphorylation in mitochondria and bacteria or photophosphorylation in chloroplasts.

779. ATPase
Definition:

An enzyme that hydrolyzes ATP into ADP and phosphate.

780. atresia
Author: Guo Li
Definition:

This is the congenital absence of or poor development of a body opening (e.g. a heart valve).

781. atretic
Definition:

Having an abnormal closure or absence of a body opening or tubular organ (e.g., a child born without an esophagus would have an atretic birth defect).

782. atrial fibrillation
Author: PharmInfoNet
Definition:

Rapid irregular twitchings of the wall of the atrium (chamber) of the heart.

783. atrial natriuretic peptide (ANP)
Definition:

This cardiac hormone (28 amino acid residues) regulates salt and water balance in body fluids and blood pressure; it has potential as a medication to treat heart and kidney failure and the buildup of excess fluid in tissue.

784. atrium (pl. atria)
Author: Guo Li
Definition:

This is upper chamber on either side of the heart. (In humans and other mammals, there are four heart chambers: two atria and two ventricles.)

785. atrium (pl.: atria)
Definition:

One of two chambers in the upper part of the heart which receives blood from another part of the body and pumps it into a ventricle (another part of the heart).

786. atrophy
Definition:

The wasting of a tissue, organ or body part.

787. atropine
Image: View the chemical structure
Definition:

A toxic alkaloid extracted from belladonna and other members of the nightshade family; it is typically used to dilate the eye and to stop muscular spasms.

788. att site
Definition:

A site on the chromosome of the bacteria E. coli where the lambda bacteriophage can insert its genome (all of its DNA) so that it can lie dormant and have its DNA reproduced whenever the bacterium reproduces for as long as the bacterium remains healthy (that is, so that it becomes lysogenic).

789. attenuate
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

Tapering gradually.

790. attenuated
Definition:

This term is used to describe a vaccine that contains live but weakened viruses that will cause the body to develop an active immunity to them but will not normally cause disease.

791. attenuation
Definition:

1. A decrease in the ability of a pathogen (like a virus or disease-causing bacteria) to cause disease.
2. The ability of a bacterium to regulate the amount of an amino acid it makes based on how much is already present, whereby excess amounts of the amino acid will turn off symthesis of itself.

792. attenuator
Definition:

An RNA sequence that regulates the expression of certain genes by terminating transcription.

793. auditory canal
Definition:

The auditory canal is the passageway in the external ear that leads to the eardrum.

794. aufwuchs
Author:
Definition:

Complex assemblage of plants and animals living on the surface of a submerged mineral or organic substrate. It includes diatoms, blue-green algae, protozoa, rotifers and nematodes.

795. augmentation mammoplasty
Author: Guo Li
Definition:

Augmentation mammoplasty is a surgical procedure to increase the apparent size of the breasts, often by using implants.

796. auricle
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

An ear-shaped appendage at the base of a leaf, leaflet or corolla lobe. Adj. auriculate.

797. auscultation
Author: Guo Li
Definition:

This is a method of clinical examination by listening to sounds produced in the body.

798. autecology
Author:
Definition:

Ecological study of a single organism or a single species.

799. autism
Author: NICHCY
Definition:

A type of pervasive developmental disorder defined by the Individuals with Disabilities Education Act (IDEA) as "a developmental disability significantly affecting verbal and nonverbal communication and social interaction, usually evident before age 3, that adversely affects a child's educational performance. Other characteristics associated with autism are engagement in repetitive activities and stereotyped movements, resistance to environmental change or change in daily routines, and unusual responses to sensory experiences." A diagnosis of autism is made when an individual displays 8 of 16 symptoms listed across three major areas: social interaction, communication, and restricted repertoire of activities and interests. (Fewer than 8 symptoms results in a diagnosis of PDD-NOS).

800. autoantibody (pl. autoantibodies)
Definition:

An antibody involved in autoimmune reactions.

801. autochthonous
Author:
Definition:

Derived from within a system, such as organic matter in a stream resulting from photosynthesis by aquatic plants. Compare allochthonous.

802. autocide
Definition:

A chemical produced by a bacteria which is toxic to other bacteria within the same species, but does not affect other bacteria.

803. autoclave
Definition:

A machine which is used to sterilize lab glassware, liquid growth media, and medical/biological/lab instruments. Essentially, it is a giant pressure cooker where the objects to be sterilized are placed inside a chamber of high temperature and pressure for an hour or more. The word is also used as a verb (as in, to autoclave something).

804. autocrine (autocrine system)
Definition:

A secretion which affects only the cell from which it was secreted.

805. autocrine factor
Definition:

A type of growth factor secreted by a cell. It is thought that autocrine factors are produced in response to infection by viruses. The secretion of autocrine factors is an important step toward developing cancer.

806. autoecious
Definition:

Term used to describe a parasite that uses only one host for its lifecycle. Compare heteroecious.

807. autogamous
Author: Mirrored from Dave Sutton's Aquatic Plant Glossary
Definition:

Relating to or reproducing by autogamy.

808. autogamy
Author: Mirrored from Dave Sutton's Aquatic Plant Glossary
Definition:

Self-fertilization, pollination of a flower by its own pollen.

809. autogenous control
Definition:

Regulation of how much a gene gets transcribed by the gene's own products.

810. autograft
Definition:

Tissue (such as skin, bone or muscle) taken from one part of a person's body and grafted to another part to replace damaged critical areas. For instance, surgeons may remove muscles from the back to replace damaged muscles in the lower leg or forearm.

811. autoimmune
Definition:

A condition where the body's immune system is unable to distinguish between foreign particles and the body's own cells and as a result attacks normal body tissue.

812. autoimmune disease
Author: PharmInfoNet
Definition:

Disorder of the body's immune system in which the immune system mistakenly attacks and destroys body tissue that it believes to be foreign. insulin-dependent diabetes is an autoimmune disease because the immune system attacks and destroys the insulin-producing beta cells.

813. autoimmunity
Definition:

A condition in which an individual's immune system starts reacting against his or her own tissues, causing diseases such as lupus.

814. autologous transfusion
Author: Guo Li
Definition:

This is transfusion of an individual's own blood into his or her body (with the blood collected from that patient several weeks before surgery). Exogenous erythropoietin can be used to promote blood formation prior to the harvest of autologous blood.

815. autologous transplant
Definition:

A transplant of an organ or tissue that is taken from the same individual. A person having blood taken a little at a time several months before a surgery to replace the blood they expect to lose during that surgery is a form of autologous transplant. Likewise, the use of muscle tissue taken from a person's back to surgically reconstruct their damaged hand would be another form of autologous transplant.

816. autolysin
Definition:

An enzyme which causes the cell that made it to self-destruct.

817. autolysis
Definition:

The process by which an organism digests its own cell through enzymes that are naturally present in the cell or in surrounding tissues; this normally occurs after the cell or tissue has died.

818. autonomic nervous system
Definition:

The part of the nervous system that controls involuntary bodily actions, such as breathing, heartbeat, food digestion, and blinking.

819. autonomic neuropathy (visceral neuropathy)
Author: PharmInfoNet
Definition:

A neuropathic disease of the nerves affecting mostly the internal organs such as the bladder muscles, the cardiovascular system, the digestive tract, and the genital organs. These nerves are not under a person's conscious control and function automatically.

820. autonomously replicating sequence (ARS)
Definition:

This is a chromosomal sequence that allows plasmids to replicate on their own in yeast.

821. autophagosomes
Definition:

This is the name given to the membrane-bound bodies, found inside cells, which trap and break down organelles.

822. autoplast
Definition:

A spherical, osmotically-sensitive cell that is formed from a parent cell by the actions of its lytic enzymes.

823. autopsy (necropsy)
Author: Mirrored from Guo Li's Dictionary of On-Line Medical Resources
Definition:

An examination of a dead body to determine the cause of death

824. autoradiogram
Author: ForBio Ltd.
Definition:

An experimental technique to visualize the distribution of radioactivity in a specimen. X-ray film placed in contact with the specimen is exposed by ionizing radiation, creating a photographic image.

825. autoradiography (radioautography)
Definition:

A technique that uses X-ray film to visualize radioactively labeled molecules or fragments of molecules; used in analyzing length and number of DNA fragments after they are separated by gel electrophoresis.

826. autosomal
Definition:

Of or relating to autosomes.

827. autosomal dominant (autosomal dominance)
Definition:

This is a type of genetic inheritance; a person who carries the gene on one allele will express (experience effects from) that gene. An autosomal dominant gene can be inherited from a single affected parent; both sons and daughters have an equal chance of inheriting the gene.

828. autosomal recessive
Definition:

An autosomal recessive gene is one which is required in two copies on an autosome to be active in an organism. For instance, a person who carry two copies of the same abnormal gene (in other words, this person is homozygous for the gene) will experience effects from that gene (for instance, he or she might then suffer from a disease coded by that gene). The gene can be inherited from both parents who carry the gene; sons and daughters have an equal chance of inheriting the gene.

If a person has a genetic disease but his or her parents seem normal, then this probably means that:

1. The parents of this person are heterozygous, unaffected carriers of the disease, or
2. The person inherited one copy of the gene from a parent, and the other "good" copy underwent a mutation early in the person's embryonic development

829. autosome
Definition:

A chromosome not involved in sex determination. The diploid human genome consists of 46 chromosomes, 22 pairs of autosomes, and 1 pair of sex chromosomes (the X and Y chromosomes).

830. autotroph
Definition:

An organism that "makes its own food" and does not require previously formed organic materials from the environment. Plants are classified as autotrophs because they use photosynthesis to make their own energy. Compare heterotroph.

831. autotrophic
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

Independent of other organisms in respect of organic nutrition; able to fix carbon dioxide, by photosynthesis, to form carbohydrates.

832. auxin (Agent Orange)
Image: View the chemical structure
Definition:

One of several hormones that plays a role in many aspects of plant growth and development. Auxins include indoleacetic acid, phenylacetic acid, and 4-chloro-indoleacetic acid. Commercially, auxins are used to promote root growth, to promote uniform flowering, and to set fruit and prevent premature fruit drop. Synthetic auxins such as 2,4-D and 2,4,5-T have been used as herbicides; broad-leaved weeds like dandelions are much more susceptible to auxins than narrow-leaved plants like grass and cereal crops.

The defoliant Agent Orange was a mix of 2,4-D and 2,4,5-T. 2,4-D is still in use and is thought to be safe, but 2,4,5-T was more or less banned by the EPA in 1979. The dioxin TCDD is an unavoidable contaminant produced in the manufacture of 2,4,5-T; as a result of the the integral dioxin contamination, 2,4,5-T has been implicated in leukemia, miscarriages, birth defects, liver damage, and other diseases.

833. auxochrome
Definition:

This is a group of atoms attached to a chromophore which modifies the ability of that chromophore to absorb light.

834. auxostat
Definition:

A system for a continuous culture in which a component of the system is set and the other parameters are adjusted to maintain the culture's growth.

835. auxotroph
Definition:

An organism that requires a specific growth factor (an amino acid, for example) for its growth.

836. avidity
Definition:

The strength of a bond between an antibody and its antigen. Similar to affinity among enzymes and their substrates.

837. Avogadro's hypothesis
Definition:

The hypothesis that equal volumes of two different gases at the same temperature and pressure contain the same number of molecules.

838. awn
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

A bristle-like appendage, e.g. on the tip or back of the lemma of a grass floret.

839. axenic culture
Definition:

A culture that contains only one microbial species.

840. axil
Definition:

The upper angle formed by a leaf or branch as it grows from the main axis (main stem).

841. axil
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

The angle between a leaf or bract and the axis bearing it. Adj.: axillary.

842. axile
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

In botany terminology, describes a plant part which is on an axis; of a placenta, on the central axis of the ovary.

843. axillary
Definition:

Located or growing from an axil.

844. axillary bud
Definition:

A bud located in the axil of a plant.

845. axis
Definition:

The main stem of a plant.

846. axis
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

In botany terminology: a stem, commonly used for the main stem of a whole plant or of an inflorescence.

847. axolotl (Ambystoma mexicanum)
Definition:

Ambystoma mexicanum, a type of salamander native to Mexico and the Western United States which spends all of its life underwater. Even as an adult animal, the axolotl retains many larval features, most notably its external gills: as a result the axolotl is an excellent example of the phenomenon of neoteny. The axolotl also has four legs and a tadpole-like tail and is an endangered species.

848. axon
Definition:

The threadlike extensions on a neuron, or nerve cell which conducts nerve impulses.

849. axonal neuropathy
Author: Guo Li
Definition:

This type of neuropathy is caused by nutritional deficiencies and poisoning by toxic substances.

850. axoneme
Definition:

The structure of an eukaryotic flagellum or cilium (long whiplike or hairlike appendages sometimes attached to cells), where two microtubules in the center are surrounded by nine pairs of microtubules around the outside.

851. azeotropic mixture (constant boiling mixture)
Definition:

This is a mixture of liquids in which the composition of the vapor is the same as that of the liquid phase, so it can be distilled without any change in composition.

852. azoospermia
Definition:

Absence of sperm.

853. Aztobacter (nitrogen-fixing bacteria)
Definition:

Aztobacter is a species of large, oval, aerobic Gram-negative bacteria that can fix atmospheric nitrogen if they have an energy source (often a carbohydrate) available.

854. B lymphocyte (B cell)
Definition:

A cell produced by the bone marrow which, when stimulated by an antigen, becomes either a memory cell or a plasma cell that forms antibodies against that antigen. Compare T lymphocyte.

855. Babes-Ernst granules
Definition:

Particles found in some bacteria that, when the bacteria are dyed, become a different color than the dye.

856. babesiasis (babesiosis, piroplasmosis)
Definition:

A parasitic disease affecting mammals which is caused by protozoa from the genus Babesia of the order Piroplasmida and is transmitted by ticks. The Babesia protozoa feed on the blood of mammals. Symptoms include high fever, anemia, and red urine (hemoglobinuria).

857. baccate
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

Berry-like; of seeds, having a succulent or pulpy testa; of fruits, having the seeds embedded in pulp.

858. bacilli
Definition:

Rod-shaped bacterial cells.

859. bacilliform (bacteriform)
Definition:

Shaped like bacteria: rodlike; elongated cylinders with rounded ends.

860. Bacillus
Author: Guo Li
Definition:

A class of bacteria which are rod-shaped. Belonging to this class are: E. coli, Salmonella, Shigella, Klebsiella, Enterobacter, Clostridia; of these, Bacillus Calmett-Guérin is administered for vaccination against tuberculosis; bacteria causing tetanus, diphtheria, pertussis, and tuberculosis are also rod-shaped.

861. bacillus (pl. bacilli)
Definition:

A rod-shaped bacterium.

862. Bacillus amyloliquifaciens
Definition:

B. amyloliquifaciens is a Gram-positive, rod-shaped bacterium used to produce alpha-amylase and serine protease.

863. Bacillus licheniformis
Definition:

B. lichemiformis is a Gram-positive, rod-shaped bacterium which is used in the biotech industry to produce the protease enzyme subtilisin.

864. Bacillus popilliae
Definition:

B. popilliae is a Gram-positive bacterium which attacks only the Japanese beetle (Popillia japonica) and is therefore used in some places in the U.S. to kill the beetles. When the larvae are infected, they turn white because of all the bacterial spores (endospores) that develop in the insects' hemolymph (blood equivalent).

865. Bacillus subtilis
Definition:

B. subtilis is a Gram-positive, rod-shaped, nonpathogenic bacterium which lives in soil. Its genome has been widely studied and is frequently used in genetic engineering and microbiology experiments.

866. Bacillus thuringiensis (Bt)
Author: Susan A.Hagedorn
Definition:

Bacillus thuringiensis is a bacterium that kills insects (mainly in the genera Lepidoptera, Diptera and Coleoptera) and is a major component of the microbial pesticide industry. Researchers are also investigating ways to incorporate the bacterium's insect toxins into the genomes of plants to make insect-resistant crops.

867. bacitracin (Altracin, Ayfivin, Fortracin, Penitracin, Topitracin,Zutracin)
Image: View the chemical structure
Definition:

An antibiotic that inhibits the growth of cell walls in Gram-positive bacteria.

868. back cross
Definition:

A crossing of a heterozygous organism and one of its homozygous parents.

869. back mutation
Definition:

A mutation that causes a mutant gene to revert to its original wild-type base sequence.

This is the opposite of a forward mutation.

870. backache (back ache)
Author: Guo Li
Definition: