L5_4_12_11 - For today: Ch. 12 p695-704 & 723-745 Ch....

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Unformatted text preview: For today: Ch. 12 p695-704 & 723-745 Ch. 6, p388-399 For Thursday: Chap 13 (depending on how far we get today Exam: Tuesday April 19th: one week from today. You will need to bring a Parscore pink, whole page scantron sheet to exams. These are available at the bookstore. You will need to bring a #2 pencil. You need to bring a calculator. The problem sets are your study guide. The old exam shows you what kind of problems there will be. Lipid bilayers are impermeable to many molecules cystinuria Epithelial cells use the energy stored in the Na+ gradient to transport glucose across and epithelial layer-transcellular transport 1) Glucose pumped into cell by Na+- powered symporter 2) Glucose passes out of the cell into the extracellular fluid and then onto the bloodstream down its concentration gradient by passive transport 3) The Na+ gradient driving the symporter is maintained by Na+/ K+ pumps on the basalateral surface. (keeps intracellular Na low) 6) Importance of the tight junction. Binding of transported molecules induces conformational changes in carrier proteins Carrier flips betw 2 conformational states. Outside: H and lactose binding sites are accessible to extracellular space. Loading is favored due to R144 bonding with E126, leaving E269 free for H+. Conformational change induced by lactose Inside: Unloading is favored because R144 bonds with E269, destabilizing H+. Conformational change Conformational change Lactose drives the conformational change, linking the transport of lactose to the electrochemical gradient. The Na+-K+ pump is an ATP-driven carrier protein that pumps Na+ out of the cell, and K+ into the cell A membrane potential is created by the combined actions of the Na+-K+ (3 Na out/ 2K in) pump (minor) and K+ LEAK channels (140mM intra and 5mM extra) out in out in The net efflux of K halts when the membrane potential reaches a value at which the electrical driving force on K+ exactly equals the effect of its concentration gradient--the electrochemical gradient is ZERO. No net flow of ions=equilibrium potential which can be calculated by the Nernst equation Resting membrane potential -20 to -120 mV Ion channels are highly selective for the ion that the transport My BAD K flows out Propagation of a signal in neurons involves sequential opening of voltage-gated sodium channels 3 types of channels: K+ Leak—non voltage gated Na+ V-gated---Na+ influx K+ V-gated—K+ efflux Propagation in one direction Property of Na+ V-gated channel— inactivation thru ball and chain Membrane potential back to normal due to action of the K+ leak channels and the Na/ K pump: 3Na+ out/2K+ in Neuronal signals are often initiated by ligand-gated ion channels The pore is lined by a ring of 5 transmembrane alpha-helices (one from each subunit)....
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This note was uploaded on 02/06/2012 for the course BIO 110 taught by Professor Rexach during the Fall '08 term at University of California, Santa Cruz.

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L5_4_12_11 - For today: Ch. 12 p695-704 & 723-745 Ch....

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