Biology 2382B Lecture Notes - Lecture 6: Cholesteryl Ester, Ldl Receptor, Transferrin Receptor
9 Feb 2018
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Document Summary
Pinocytosis: non-specific internalization of small amounts of extracellular molecules. Receptor-mediated endocytosis: a method of selective internalization of specific extracellular molecules (ligands: ldl (low-density lipoprotein, hormones (insulin), certain glycoproteins transferrin. Lipids are transported in large well-defined water-soluble complexes/particles called lipoproteins: protein which binds certain types of lipids (ie. cholesterols don"t want them floating) Ldl contain ~ 88% cholesteryl esters and mediates cholesterol transport: largely made of cholesterol, important for transportation. Ldl receptors on plasma membrane (localized in clathrin-coated pits) Amphipathic shell, composed of a phospholipid monolayer, and apolipoprotein. Apolar core hydrophobic, mostly cholesteryl esters. Receptors in plasma membrane recognizes a unique ligand (ldl) Experiment done at cold temperature allows particles to bind, but not taken up. Raising temperature allows bound particles to be taken up: clathrin coated pit forms, vesicles can then form, get iron-labelled ldl particles inside, once clathrin is removed: smooth-surfaced early endosome is present. Two-layer coat: clathrin and adapter protein (ap) complexes ap1-tgn + ap2-pm.
