The GoldmanHodgkinKatz equation says that the current density, I (in units of A m2 ), of Na+

The Goldman–Hodgkin–Katz equation says that the current density, I (in units of A µm−2

), of Na+

through a cell membrane can be modelled by the equation I = PN F

2V RT "

ci − cee

−V F RT 1 − e

−V F RT #

, where F is Faraday’s constant, R is the gas constant, V is the voltage difference (in V) across the cell membrane, T is the temperature (in K), and ci and ce are concentrations (in mol/L).

a. What are the units of PN ?

Make sure you give all the working, and all the reasons, for your answer.

Don’t just write down the answer: it’s the working that is important, here, not the actual answer.

b. What is the value for V that gives zero current?