## The Nernst Equation

Remember what happened when we specified that the membrane should only be permeable to ONE ion (in this case K+):

Here is an even simpler way of stating the same thing, called the "Nernst Equation", and as an added bonus I'll even let you in on the value of the mysterious "k":

This equation was actually discovered half a century *before* the Goldman equation, by a Nobel prize winner named Walther Nernst -- hence, the Nernst equation. "C" in the standard version stands for "concentration". I included the second version just to make the relationship between the Nernst and the Goldman equations more apparent.

By the way, **the value of K = 62 is valid only at body temperature (37 degrees Celsius). **A deep sea fish would have a different value, because of the lower effect of temperature on the potential energy of the ions !

Copyright University of Maryland, 2007

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