Membrane Structure Flashcards
Fluid mosaic
Allow proteins to move laterally. Bc of non-covalent bonds such as van deer wale and hydrophobic effects.
Selectively permeable barriers
Micelles
Form if the cross sectional area of the polar group is greater than that of the acyl side chain
Bilayer
Forms if non polar and polar regions have similar areas
Liposome
Hollow vesicles where unstable bilayer folds back on itself
-will form when dispersed in aqueous medium
The most abundant lipid in cell membranes
Phospholipid
Phospholipids
2 hydrophobic fatty acid chains linked to phosphate-containing polar head
2 chains can differ in length and saturation.
Presence of double bond causes a kink
Glycerol phospholipids
Fatty acids attached to each of the first 2 carbons of glycerol via ester bond and a phosphate group attached to 3rd carbon
-named based on alcohol group attached to the phosphate in polar head
Sphingolipid
Phospholipid. Contain sphingosine(amine alcohol w long hydrocarbon chain)
-ex is sphingomyelin (contains phosphate polar head)
Glycolipids
Lipids containing a carbohydrate moiety
Cholesterol
Amphipathic sterol.
Too hydrophobic to form bilayer on their own
-ensures fluidity by preventing phospholipids from packing too closely.
-maintain rigidity and decrease permeability
Inner leaf
Phosphatidylethanolamine, phosphatidylserine, phosphatidylinositol (signaling)
Outer leaf
Phosphatidylcholine, sphingomyelin, glycolipids
Lower temperatures
Gel state, fatty ache chains packed closer, fluidity decreased
Temperature increases
Fluid state. Energy to overcome forces, thickness of bilayer decreases, fluidity increases
Lipid raft
Cholesterol, sphingolipids, phospholipids, and saturated tails are closely packed and less fluid, create these
Play role in signal transduction
Flippase
Transfer lipids to other leaf. Outside to inside
ATP dependent. Occurs slowly (24hr)
Floppases
ATP dependent, from cytoskeleton to extracellular. Inside to outside
Scramblases
In either direction along concentration gradient.
No ATP required, activity increases when intracellular Ca increases
Integral proteins
Inserted in membrane. Span bilayer. Covalently attached to leaflet. Only released by disrupting bilayer with detergents or organic solvents
Peripheral proteins
Associated w integral and membrane lipids by non covalent bonds. Can be removed without disrupting bilayer by high salt or extreme pH
Porins
Transmembrane proteins which multiple B strands fold into barrel conformation, inside is hydrophilic and allows small solutes and ions to cross the membrane
