Organelles

2 membranes which create three spaces:

1. The cytoplasm
2. The intermembrane space
3. The inner mitochondiral matrix

The mitochondria is the site of aerobic metabolism. The citric acid cycle crackles along in the inner matrix, producing electron donators that reduce the cytochrome enzymes in the inner membrane proteins, which pumps hydrogen ions into the intermembrane space to power ATP synthase.

The inner matrix is also the site of beta-oxydation and haem synthesis.

Structure:

5nm thick membrane

Lipids (50%):

• Phospholipid Bilayer, polar phosphate group and nonpolar fatty acid tail;
• Choelsterol, provides rigidity

Proteins (50%)

1. Surface proteins
2. Receptors → Δ cell fn when bound by ligands
3. Enzymes → Catalyse reactions
4. Cell adhesion molecules → anchor cells to neighbours or basal laminae
5. Integral Proteins → provide stability
6. Transmembrane Proteins
7. Ion Channels/Carriers → passive transport
8. Pumps → active transport; maintain homeostasis

Function:

• Barrier function
• Selective permeability (e.g. to glucose)
• Signal transduction

Structure

• Inner and outer nuclear membrane with nuclear pores
• Nucleoplasm consisting of hetero- and euchromatin
• Nucleolus, site of manufacture of ribosomes and RNA

Function

• Concentrates and maintains DNA
• Regulates gene expression

Endoplasmic reticuluum: 3d mesh of membranous sheets. RER bears ribosomes and is site of most protein transcription. SEM is site of phospholipid and steroid manufacture.

Golgi apparatus: Stacked cysternae which gives off vesicles. Post-transcriotion modification of proteins. Prepares proteins for exocytosis.

Cytoskeleton: Provides structure, contributes to motility.