BIO 365R Homework I answers

BIO 365R Homework I - 4 If the membrane were solely permeable to Cl the membrane potential would be E cl = 58-1 log[Cl out[Cl in or-58 log(300/400

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Imagine a cell with the following intra- and extracellular ion concentrations: Intra (mM) Extra (mM) Na + 200 200 K + 200 20 Ca 2+ 10 100 Cl - 400 300 A - 40 100 1) If the membrane were solely permeable to K + , the membrane potential would be: E K = 58 log [K out ]/ [K in ] or 58 log (20/200) or 58 (-1) = -58 mV 2) If the membrane were solely permeable to Na + , the membrane potential would be: E Na = 58 log [Na out ]/ [Na in ] or 58 log (200/200) or 58 (0) = 0 mV 3) If the membrane were solely permeable to Ca 2+ , the membrane potential would be: E ca = 58/2 log [Ca out ]/ [Ca in ] or 29 log (100/10) or 29 (1) = 29 mV
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Unformatted text preview: 4) If the membrane were solely permeable to Cl-, the membrane potential would be: E cl = 58/-1 log [Cl out ]/ [Cl in ] or -58 log (300/400) or -58 log (0.75) = 7.24 mV 5) If the membrane were permeable to BOTH Na + and K + but is 10x more permeable to Na + than K + . E m = 58 log [(10)200 + 20] / [(10)200 + 200] = 58 log 2020/ 2200 = 58 log (0.91) = -2.1 mV (here E m refers to the membrane potential as it is no longer determined by the equilibrium potential for a single ion)....
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This note was uploaded on 04/12/2009 for the course BIO 51340 taught by Professor Zakon during the Spring '09 term at University of Texas at Austin.

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