Molecular Biology of the Cell 6th Edition

Published by Garland Science
ISBN 10: 0815344325
ISBN 13: 978-0-81534-432-2

Chapter 11 - End-of-Chapter - Problems: 11-3

Answer

Nernst Equation: $-RT/nF *(ln (c_{o} / c_{i}))$

Work Step by Step

Membrane potential considering only K+ ions: 58*log(9/344) =58*log(0.026) =58*-1.585 =-91.93mV =-92mV This is closer to the resting membrane potential. Membrane potential considering only Na+ ions: 58*log(65/430) =58*6.615 =58*0.82 =47.56 mV =48 mV This value is closer to the action potential. This occurs because there are numerous leak K+ channels that allow K+ to leak untill the potential gradient cannot oppose their movement. Thus, this value is closer to the resting potential, and the Na+ channels only open when they are stimulated to be; that is, when the influx of Na+ reverses the potential of the membrane and therefore causes the neighboring Na+ channels to open. This stimulates the action potential.
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