BIO 320 Lecture Notes - Lecture 15: Endothelium, Ldl Receptor, Copii
Document Summary
Pinocytosis (drinking), constitutive and non-selective: a. clathrin-mediated, b. caveolin-mediated. Receptor-mediated endocytosis, also clathrin-mediated, but is selective. Phagocytosis (eating): most endocytic vesicles fuse with the (early) endosome. Pinocytosis: virtually all eukarotic cells continually internalize portions of their plasma membrane as clathrin-coated pinocytic vesicles. These small vesicles bring in fluid from outside the cell (a. k. a. , fluid-phase endocytosis), allowing cell to sample soluble components of the extracellular environment. This sampling is important in some specialized cell types (e. g. , dendritic cells of the immune system). It also leads to recycling of membrane from plasma membrane: clathrin-mediated pinocytosis. Dynamin helps to pinch off the clathrin-coated vesicle, which fuses with (early) endosome after uncoating. It does not dissociate from vesicles (i. e. , no uncoating). Caveolae( little cavities ) form from lipid rafts on plasma membrane. Dynamin also helps to pinch off the caveolae. Clathrin participates in endocytosis in at least 2 ways. Pinocytosis: nonselective uptake of extracellular fluid in the lumen of clathrin-coated vesicles, occurs continually.
