CAS NE 102 Lecture Notes - Lecture 8: Archean, Hydrophile, Detergent
20 Jul 2016
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Document Summary
Membrane proteins: most membrane functions are carried out by membrane proteins. Proteins constitute 50% of the mass of most plasma membranes remainder is lipid and small amounts of carbohydrate found on some lipids (glycolipids) and many of the proteins (glycoproteins) Lipid molecules are much smaller than proteins, so cell membrane contains 50x more lipid molecules than protein molecules. Membrane proteins can be associated with the lipid bilayer in different ways: (pic above: transmembrane proteins: amphipathic (both hydrophobic and hydrophilic parts). Extend across bilayer as a single alpha helix, multiple alpha helices, or as rolled-up beta sheet (b. Barrel: monolayer-associated alpha helix: anchored to the cytosolic half of the lipid bilayer by an amphipathic alpha helix, lipid-linked: linked to either side of the bilayer by covalently attached lipid molecule (red zigzag lines). Phosphate is charged protein won"t become transmembrane if phosphorylated. D) protein-attached: attached to the membrane by weak, noncovalent interactions with other membrane proteins.
