In our derivation of the Nernst potential we made several assumptions, one of which was that the concentration of the permeant ion(s) on each side of the cell membrane did not change as the problem went to completion. Assume a cylindrical cell of radius R meters and length L meters, having a membrane capacitance Ca farads/m2, one singly-charged permeant species, X, with an intracellular concentration of [X]i mol/L and an extracellular concentration of [X]o mol/L (assume that [X] > [X], so that some X moves out of the cell to