BIOS 281 Lecture 3 Membrane Transport and Potentials

requires one to two thirds of cells energy ac0ve

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Unformatted text preview: n of concentrated urine. Ac0ve Transport •  REQUIRES energy •  Moves substances AGAINST concentra0on gradient –  Primary Ac0ve Transport –  Secondary Ac0ve Transport –  Co- Transport, Counter- Transport Ac0ve Transport Primary Active Transport •  Molecules are “pumped” against a concentration gradient at the expense of energy (ATP) – direct use of energy Secondary Active Transport •  Transport is driven by the energy stored in the concentration gradient of another molecule (Na+) – indirect use of energy Ac0ve Transport Examples 1. Na+-K+ ATPase •  Carrier protein located on the plasma membrane of all cells •  Plays an important role in regulating osmotic balance by maintaining Na+ and K+ balance (inhibition by ouabain causes cells to swell and burst!) •  Requires one to two thirds of cells energy! Ac0ve Transport Examples 2. Ca2+ ATPase •  Present on the cell membrane and the sarcoplasmic reticulum •  Maintains a low cytosolic Ca2+ concentration 3. H+ ATPase •  Found in parietal cells of gastric glands (HCl secretion) and intercalated cells of renal tubules (controls blood pH) •  Concentrates H+ ions up to 1 million-fold Secondary Ac0ve Transport •  In some cases, same as co- or counter- transport 1.  Co-transport (co-porters): substance is transported in the same direction as the “driver” ion (Na+) Examples: outside N a+ AA Na+ gluc Na+ 2 HCO3- Secondary Ac0ve Transport 2. Counter-transport (anti-porters): substance is transported in the opposite direction as the “driver” ion (Na+) Examples: outside N a+ N a+ Ca2+ Na+/HCO3- H+ Cl-/H+ So what? •  Understanding what is in the cell and how it moves in and out can be a tremendously helpful pharmacological tool. •  Glycosides: class of compounds/drugs that increase cardiac contrac0lity. –  What does that mean? –  When might this be used? •  Glycosides INHIBIT the NaKATPase –  –  –  –  Increase intracellular Na Decrease Na gradient Decrease Na/Ca counter- transport Increase intracellular Ca •  What does this do? Q: How do cardiac glycosides increase cardiac contractility? Na+ Na+ K+ Na+ Ca++ Digoxin has been a cornerst...
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This note was uploaded on 11/12/2013 for the course BIOS 281 taught by Professor Varamini during the Fall '12 term at Biola University.

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