Atoms: nucleus with + protons & neutral neutrons with - electrons orbiting around the + nucleus

Neural atom: proton nos=electon nos

Atomic electrons: orbiting in different shells around nucleus; 1st shell 2e; 2nd shell 8e

Stability reached: electron outer-most shell is filled or complete with all required electrons

Inert elements: natural atoms with complete electron outer shell

Ions: non-neutral atoms with charges - postive: lacking electrons; negative: excess electrons

Bonding: merge of electrons to form complete & hence stable outer electron shells for all ions involved

Element: only one kind of atom; cannot be broken down into other substances

Periodic Table of elements: listing of elements according to atomic no. (no. of protons in the nucleus); about 90 occurs in nature, others artificial

Elements: symbols; C, H, N, O (~96%), others (3.9%), trace (<1%)

Molecule: two or more atoms bonded together, either same elements or different elements

Compound: bonded atoms of different elements

Valence electrons: electrons in the outer shell

Bonds: single bond - involving one electron from each atom (H2O); double bond - involving 2 electrons from each atom (O2)

Bonds: sharing of electrons - 1) ionic bonds; 2) covalent bonds; 3) hydrogen bonds (much weaker than ionic or covalent; responsible for linking two or more molecules)

Covalent bond: equal sharing (non-polar) of valence electrons to form complete outer shell for each of the atoms involved (eg. methane CH4) - single bond: methan CH4; double bond: oxygen gas O2; nitrogen gas N2

Polar covalent bond: non-equal sharing of valence electrons; one electron spends more time orbiting one atom than the other; s.t. one atom (hydrogen) has slight positive & the other (oxygen atom) slight negative charge (more electron time, rather than neutral charge); e.g. water molecule (polar molecule): with polar angle=104.5

*Electronegativity: the ability of an atom to attract electrons from other atoms --> e.g. NH3 where N atom is more electronegative (shared electrons spend more time around N atom than H atom) due to polar covalent bond

Ionic bond: formed by one atom GIVING up electron(s)) in incomplete outer shell to another atom s.t. all atoms form complete outer shells --> this is Not Sharing of electrons as atoms either gives up or gains electrons --> hence, the stable atoms now have net charges instead of neutral charges in covalent bonds --> they form ions --> e.g. NaCl: Na+, Cl-

*Hydrogen bonds: due to polar covalent bonds of hydrogen (slight +: ++) with oxygen --; the hydrogen atom can form weak electrical attraction with other ++ atoms; hydrogen bond - weak electrical attraction between an electronegative atom & a hydrogen atom (++) bonded to another electronegative atom

Chemical formula: CO2, O2, H2O, NH3

*Structural formula: shows all atoms (nos, elements) & nos. & type of bonds

Organic compound: molecules of different elements, mainly CARBON; occur naturally in living things; other elements - oxygen, nitrogen, hydrogen, sulfur & phosphorus

Inorganic compounds: usually no carbon, except carbon gases (carbon monoxide, carbon dioxide); but still essential to living things

*Importance of water: 70% of animal cells; essential properties --> cohesion --> adhesion --> ability to store heat

Cohesion of water: weak hydrogen bonds btw ++H atoms & electronegative --O atoms --> enables water moelcules to form hydrogen bonding with one another --> cohesion enables water to form rivers & form drops

Heat storage: energy stored with the hydrogen bonds between water molecules --> hence, body heat is stored within these hydrogen bonds --> boiling water: makes water molecules move faster --> means breaking the hydrogen bonds --> energy is required to break these bonds --> enables organisms to survive when environment changes

Adhesion: ability to stick to others --> due to polar water molecules, its hydrogen bonding is conducive for bonding to other --atoms --> hence, suitable as a solvent: substance in which others are dissolved --> e.g. NH3 (ammonia) dissolves readily in water due to ++H & --N atoms

Ionic adhesion: water can readily dissolve common salt NaCl --> Na+ to --O & Cl- to ++H

Capillary action: tendency of water to move thin tubes due to adhesion of water --> plants use capillary action to transport water from roots to leaves

Animal cells: 70% water, 1% trace (Mg+, Zn+, Ca+) & 29% organic compunds --> lipids, nucleic acids, proteins & carbohydrates

Carbohydrates: energy-storing compounds of life --> sugars --> ratio C:H:O = 1:2:1 --> simplest type: monosaccharide --> commonest monosaccharide: glucose C6H12O6

Disaccharide (Maltose): two sugar glucose formed by dehydration synthesis (reaction in which two molecules are bonded together by the removal water molecule during the process) --> enabled by enzymes actions

Polysaccharides: >=2 saccharides formed --> starch in plants --> glycogen in animals --> cellulose in plant shells --> no limit to saccharides in polysaccharides

Hydrolysis: process by which molecules are disassembled by the addition of water moelcules through the actions of enzymes --> polysaaccharides into glucose units

Lipids: insoluble organic compounds --> e.g. fats, oils, phospholipids, streoids (cholesterol) --> simple fat: made from dehydration synthesis of 1 glycerol molecule + 3 fatty acid molecules (carboxyl group + carbon chain)

Lipids: importance energy-storing molecule --> 1 fat molecule = 2*carbohydrate molecule energy

Lipids: grouped by nos. of carbon bonds --> single C-C bond: saturated fats (BAD, oil at toom temperature, red meat & diary products, increase blood cholesterol) --> double C=C bond: unsaturated fats (GOOD, partial or solid at room temperature, decrease blood cholesterol) --> polyunsaturated fats: more than 1 C=C bond in a fatty acid chain --> hydrogentation: unsaturated fats into saturated fats by addition of hydrogen atoms

Proteins: structure & function of cells --> types: structural proteins (collagen), transport proteins (hemoglobin), enzyme, antibodies --> 1 protein molecule = 1 carboxyl group + 1 H + 1 amino group + 1 side chain (any type of groups)

Amino acids: building blocks of proteins --> 20 types of amino acids in proteins

Proteins synthesized by dehydration between 1 carboxyl group & 1 amino group --> loss of 1 water molecule in the process --> 1 bond: peptide --> 2 chain: dipeptide --> many chains: polpeptide

Enzyme: speed up chemical reactions --> catalyze of digestion, synthesis of molecules & storage & release of energy

Nucleic acids: 2 types --> DNA & RNA

DNA: hereditary materials --> information to form organism proteins --> Nucleotide

Purines: A & G

Pyrimidines: T & C

A=T: double hydrogen bonds

C=-G: triple hydrogen bonds

RNA: helps form proteins from DNA --> turn info. in DNA into proteins --> single-stranded --> ribose --> A=U: Uracil