BIO 320 - CELL BIOLOGY Lecture 9 (02/16/2010). Endocytosis And Exocytosis Reading: Alberts, 5th Ed. Pages 799-809 Endocytosis : Cellular Uptake of Particles and Macromolecules A. Phagocytosis is the cellular uptake of particulate matter from the environment. B. Endocytosis is the cellular uptake of material dissolved or suspended in fluid. 1. Bulk-phase endocytosis does not require binding to the surface membrane. 2. Receptor-mediated endocytosis (RME) follows the specific binding of substances to membrane receptors. a. Ligand-bound receptors collect in specialized regions of the membrane forming coated pits . The sorting signal appears to be a key tryosine in the cytoplasmic tail of receptors. b. Clathrin-coated regions invaginate into the cytoplasm, forming coated vesicles . c. Clathrin contains three chains that form a triskelion capable of changing from a flat
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