Week 4 MPW Lecture 9

Question 1

The membrane potential for potassium was -95 mV, and the membrane potential for sodium was +67 mV. Why is the absolute size of the potential larger for potassium (ie 95 compared to 67)?

Answer 1

This was not intended to be a trick question, just to make sure that you actually understand it (rather than merely being able to use the equations). Basically, because the ratio of ion concentrations is greater for potassium (140/4) than it is for sodium (150/12).