Membrane Structure Overview
PLASMA MEMBRANE
- Phospholipid bilayer: bilayer that comprises mostly phospholipids
- Fluid mosaic: mosaic of proteins embedded within a fluid phospholipid bilayer
- Selectively permeable: some substances move through passively, others use proteins for transport
- Phospholipids
- Proteins
- Cholesterol
- Carbohydrates
- Amphipathic: hydrophilic head and hydrophobic fatty acid tails
- Form liposomes in aqueous environment
- Weak hydrophobic interactions = membrane fluidity
- Saturated phospholipids: maximize hydrogens in fatty acid tails, no kinks
- Unsaturated phospholipids: double bond produces kink, increases fluidity
- Temperature buffer
- Moderate temperature: decreases fluidity, lessens lateral movement
- Low temperature: increases fluidity, prevents solidification
- Includes transmembrane proteins that span the bilayer (other types exist)
- Proteins provide about half the mass of the membrane
- Glycoproteins: branched carbohydrates covalently bound to proteins
- Glycolipids: carbohydrates covalently bound to lipids (extracellular only)
Blood types
- Carbohydrates on surface of red blood cells must be compatible between donor & recipient in blood transfusion
- Cell communication
- Import and export of molecules
- Cell growth
- Cell motility
- Cell motility