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College of Computer, Mathematical and Natural SciencesBSCI201Human Anatomy and Physiology IOpoku-EduseiChapter Three Notes1.Passive Process: Filtrationa.A passive process- no energy input b.Movement of solution from are of higher pressure to area of lower pressure; down a pressure gradient 2.Active Processes a.Energy (ATP) is required for the movement of substances across the plasma membrane b.2 types: Active transport and Vesicular transport c.Active transport- movement of solutes/ions from area of lower solute concentration to is of higher solute concentration (against a concentration gradient); mediated by carrier proteins. Active transport exhibits saturation and specificity. Because ions are charged, carrier proteins are required c.i.Ex. Sodium/potassium pump (Na+/K+ pump)c.ii.Hence, active transport is also known as “Solute Pumping” d.Active Process- Vesicular Transport d.i.2 types- Exocytosis and endocytosisd.i.1.Exocytosis- movement of substances enclosed in vesicles from the interior of cells to the exterior. Hormones, enzymes are secreted via Exocytosisd.i.2.Endocytosis- movement of substance from the exterior of cells to the interiors- 3 typesd.i.2.a.Phagocytosis- movement of solid particles from the exterior into the cell; solid particles are enclosed in vesicles called phagosomes; lysosomes fuse with the phagosomes to digest the phagosomes and its contents. Lysosomes contain powerful digestive enzymes called lysozymes. Lysozymes digest the content of the phagosomes. Cells that perform Phagocytosis are called phagocytes d.i.2.b.Pinocytosis- (aka bulk flow endocytosis) movement of solution into cells from the interstitial fluid by enclosing the solution in vesicles. All cells in the human body undergo Pinocytosis- that’s how cells obtain nutrients. d.i.2.b.i.Pinocytic vesicles- vesicles containing solution – fuse with lysosomes and the pinocytic vesicles are partially digested to release the solution into the cell d.i.2.c.Receptor-mediated endocytosis- substances bind to specific receptors on the surface of the cell;
clathrin appear where the substances are bound; coated pits form to transport substances into the celld.i.2.c.i.Exhibits saturation and specificity d.i.2.c.ii.LDL is taken into steroidogenic cells via receptor-mediated endocytosis- steroidogenic cells express LDL receptors. Hence, receptor-mediated endocytosis exhibits saturation and specificity 3.Transcytosis and Vesicular traffickinga.Transcytosis: movements of substances enclosed in caveolae into a cell, across the cell and released on the opposite side of the cell via Exocytosisa.i.Ex. Substances in the blood stream are moved into endothelial cells via endocytosis and then are moved across the cell to the opposite side and released via Exocytosis to underlying tissuesb.Vesicular trafficking: intracellular movement of substance from one organelle to another within the cell.

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