Membrane Structure and Function

cell biology exam 3

plasma membrane

the protein containing lipid bilayer that surrounds living cells

• in all cells

• allows the composition of cell to be different from its environment

• self healing

• composed of lipids and forma bilayer

membrane structure

• phospholipid bilayer

• form = function

• allow nutrients in and waste out

• functions to allow the cell to move and change shape

• self healing

lipid bilayer

thin pair of closely positioned sheets composed mostly of phospholipids that forms the strcutured basis of all cell membranes

amphipathic

having hydrophilic and hydrophobic regions

• the reason why membranes assemble into bilayers

• polar head groups form electrostatic interactions with water (also what heals the membrane)

• hydrophobic regions cluster away from water forcing water molecules around them to rearrange

phospholipids

class of molecules that make up most of the lipids in the bilayer

• composed of two fatty acid tails linked to a phosphate containing polar group

• different ones have different features and purposes in membranes

self healing nature of the membrane

• tear in membrane, creates a region where the hydrophobic tails are exposed to water

• this is a high energy, unfavorable arrangement the lipid bilayer will spontaneously

flippases

help lipids flip from the outer layer to the inner layer

• has preference for phosphatidyl serine and phophatidylethanolamine)

• require ATP

floppases

help lipids flop from the inner layer to the outer layer

• has preference for phosphatidylcholine, sphingamyelin, and cholesterol)

• require ATP

scramblases

• can do either

• flippase or floppases

membrane proteins

any proteins associated with the lipid bilayer of the cell membrane