File:Cell-membrane-electrochemical.PNG

Summary

 * Cell membrane while showing the passage of Sodium ions and Potassium ions in Sodium Potassium pump.
 * The following image was obtained from Media portfolio website of Hill and Petrucci book of General Chemistry, available on http://cwx.prenhall.com/bookbind/pubbooks/hillchem3/medialib/media_portfolio/18.html

Fair use for image:Cell-membrane-electrochemical.PNG
The image linked here is claimed to be used under fair use as:
 * 1) it is a scientifical significant diagram of a well known biological process;
 * 2) the photo is only being used for informational purposes.
 * 3) Its inclusion in the article adds detailed information to it, because it shows how the gradient of ions in and out the cell constitutes a concentration cell in biological organisms, thus Nernst equation is used to calculate the potential involved in the cell, and how the scientific nature of the process would be easily understood to the general public.