Biology 2382B Lecture Notes - Lecture 6: Cholesteryl Ester, Ldl Receptor, Transferrin Receptor
16 Aug 2017
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Delivery of membrane and cytosolic proteins for degradation in lysosomes. Chapter 14: receptor mediated endocytosis, ldl receptor, transferrin cycle p. 659-664; Phagocytosis macrophage (immune cell) recognize bacteria and engulf/digest it: very extreme example of internalizing extracellular material, not specific. Pinocytosis sipping: small indentations on the membrane take in a small amount of extracellular fluid. Receptor-mediated endocytosis a method of selective internalization of specific extracellular molecules (ligands: ldl (low-density lipoprotein, transferrin, hormones (e. g. insulin), certain glycoproteins, etc. Lipids are transported in large well-defined water-soluble complexes/particles called lipoproteins. Ldl contain approx 88% cholesteryl esters and mediate cholesterol transport. Ldl receptors on plasma membrane (localized in clathrin-coated pits). Amphipathic shell, composed of a phospholipid monolayer, and apolipoprotein b (belt): outer portion of phospholipid is polar interact with water. Inner portion of phospholipid is hydrophobic associate with cholesterol. Apolar core hydrophobic, mostly cholesteryl esters. Cholesterol = major source for making membranes & insulated sheath around neurons.
