L22: Biological membranes Flashcards
What are the two major components of all membranes?
lipids and proteins
What must membranes be in order to function properly?
- flexible
- semi-permeable
- self-sealable
What are the functions of biological membranes?
- define external boundaries
- control molecular traffic
- divide cells-organelles
- organize rxn sequences (enzyme pathways)
- cell-to-cell communication
- transporters, receptors, adhesion molecules
- energy transduction within the cell
fatty acids and lysolipids are ____ shaped
wedge (head greater than side chain)
Glycerophospholipids and sphingolipids are _____ shaped
cylindrical (head equals side chain)
What makes the lipid bilayer asymmetrical?
there are different binding sites for proteins/enzymes as well as sites for modification and binding of signaling proteins
proteins make up to ___ of the membrane
80%
how/why are integral proteins removed?
They are removed using detergents and are removed for studying purposes
Amphitropic proteins can ____
interact reversibly with the membrane (can be removed or bound to the membrane)
What is topology?
it is the 3D relationship of a molecule to the membrane
What is the hydropathy index?
it is the delta G of the transfer of an AA side chain from a hydrophobic solvent to water
what are the delta G conditions for the hydropathy index?
delta G < 0 = hydrophilic (favorable)
delta G > 0 = hydrophobic (unfavorable)
What is a hydropathy plot?
it plots hydropathy index vs. residue number
how many angstroms are there for every AA that is added per helix?
1.5
What are the topology rules?
- positive inside rule (positively charged AAs are located on the inside
- Tyrosine and Tryptophan are found at the membrane surface
