Imagine a cell with a semi-permeable membrane that is selective to K + ions only. The internal solution contains 100 mM KCl and the external solution contains 1 mM KCl. What equation would you use to determine the potential (EK) developed across the membrane?

Ek = (RT/zF) * ln ([k+]o/[K+]i)

Explanation:

R = gas constant (8.31 J/Kmol)

T = Temperature (k)

F = Faraday constant (9.65 * 10exp4 coulomb/mole)

z = valence of the ion (1)

[k+]o = Extracellular K concentration in mM

[K+]i = Intracellular K concentration in mM

ln = logarithm with base e