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PHOSPHOLIPID BILAYER Outer leaflet: CHOLINE, SPHINGOMYELIN! o Glycolipids, Phosphatidylcholine and sphingomyelin Inner leaflet: ETHANOLAMINE, INOSITOL, SERINE o Phosphatidylethanolamine, Phosphatidylinositol, and phosphatidylserine o Net negative charge on cytosolic face of PM. Cholesterol- stiff molecule, provides structural component to membrane o Rigid ring structure, affects membrane fluidity depending on temp. Hot- reduces fluidity and permeability Cold- prevents freezing and increases fluidity. Interior of bilayer is hydrophobic, so membrane impermeable to water-soluble molecules. Bilayers are viscous, not solid. MEMBRANE PROTEINS 2 classes: 1. Peripheral o Proteins that dissociate from the membrane if salt added or pH changed. . o Attached to membrane proteins. 2. Integral o Proteins BURIED in membrane (via hydrophobic residues) o Most do not move b/c attached to filaments in the cell. o Need detergents to remove 3. Anchored o Can move around on membrane o Buried in ONE leaflet of PM Porins do not have alpha helical regions. They have beta sheets that make an aqueous pore. GPI-anchored proteins are on OUTSIDE of membrane Myristic acid (14C), prenyl groups, and palmitic acid (16C) are on inner leaflet of PM. o Proteins targeted to PM by positively charged regions of polypeptide chain or attached lipids. + charge interacts with negative charged phosphatidylserine on inner face. Membrane proteins can move LATERALLY in membrane o FRAP Stain cell, destroy proteins on cell, eventually other membrane proteins move laterally to replace the destroyed ones and the entire cell becomes fluorescent again. Studies rate of diffusion
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This note was uploaded on 03/19/2008 for the course MMG 409 taught by Professor Arvidson during the Spring '08 term at Michigan State University.

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