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Unformatted text preview: September 21 st Lecture Notes: Membrane Proteins (Ch. 11 still): carry out most membrane function o transport ions and particular nutrients across the membrane (allow polar molecules to pass through the hydrophobic interior of the membrane) o anchor the membrane to macromolecules on either face (cytoskeleton, connect cells together in tissues) o act as receptors for chemical signals (extra-cellular domain binds with a ligand, triggers a conformational change in the cytosolic face, thus triggering a signaling pathway) o act as enzymes to catalyze certain reactions can associate with the lipid bilayer in various ways o transmembrane proteins (cross through the bilayer, have both hydrophilic and hydrophobic regions) o membrane-associated proteins (associate with the inner leaflet of the bilayer with an exposed amphipathic alpha-helix on the protein surface) o lipid-linked (attached covalently to lipid groups) o o roughly classified as INTEGRAL (can be removed only with detergents) or PERIPHERAL (can be separated with gentler methods) cholesterol presence: cholesterol is largely absent in intracellular membranes, but makes up approximately half of the total surface area of a plasma membrane membrane protein concentration / overall membrane composition depends on the...
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