The Nucleus
- consists of the nuclear membrane with nuclear pores, nucleoplasm, and chromatin. A specialized region called the nucleolus is where ribosome subunit assembly occurs.
Chromatin describes the genetic content (DNA and proteins) in a non-dividing cell. During division, condensation allows individual chromosomes to be seen.
Ribosomes
-very small and numerous, constructed in the nucleolus, exported to cytoplasm
-made of ribosomal RNA and riboproteins - two subunits- large and small
-function as workbench for protein synthesis (more on this later!)
- may be free (suspended) in the cytosol or bound to the rough ER
The endoplasmic reticulum (ER)
-continuous with nuclear membrane
Rough ER functions in membrane production, protein modification and trafficking.
Smooth ER functions in lipid synthesis, carbohydrate metabolism in liver, detoxification of drugs and alcohol (in liver), and as a calcium ion reservoir in muscle cells.
The Golgi body
-organizes, modifies, stores, and routes products of the ER. The Golgi body can alter membrane proteins (glycoproteins), manufacture macromolecules (hyaluronic acid), and target products for export within and outside the cell.
Lysosomes
-contains hydrolytic enzymes to break down all classes of macromolecules
-pH (5) is much lower than cytoplasm
-originate in the Golgi body
-function in catabolism (intracellular digestion), organelle recycling, and cell death
Vacuoles
-larger than a vesicle
-surrounded by membrane called the tonoplast
Food vacuole-formed during phagocytosis
Contractile vacuole-pumps excess water from fresh-water protozoa (eg. Paramecia sp.)
Central vacuole - in plants, serves as storage for organic and inorganic ions, contains hydrolytic enzymes, keeps dangerous by-products from cytoplasm, may contain pigments (in flower petals), important in plant growth and cell shape.
Peroxisomes
-found in nearly all eukaryotic cells. Breaks down hydrogen peroxide and helps to detoxify poisons. Breaks down fatty acids to two carbon fragments.
The mitochondrion (the mighty mitochondrion)
-enclosed by a double membrane, has own circular DNA (but just mommy's) and ribosomes and its own genetic code. Can grow and reproduce autonomously. Thought to have origins with photosynthetic bacteria (endosymbiotic theory). Inner membrane (cristae) is highly convoluted containing enzymes essential for aerobic respiration.Two compartments include the intermembrane space and the inner compartment (matrix). The matrix contains enzymes for aerobic respiration
The mitochondrion produces the majority of ATP yield from the oxidation of organic molecules.