4 What is the membrane potential Vm of a cell with 20 open K

4. What is the membrane potential (Vm) of a cell with 20 open K+ channels and 40 open Na+ channels. Assume EK is -85 mV and ENa is +30 mV.

Solution

Pmf = (electric potential) - ZpH

Electric potential = cytoplasm - matrix

It means (-85-30) as potassium remains outside as it is impermeable to inner membrane..

Z= 2.303 RT/F = 59mV at 25°C

Putting in the equation

Pmf = - 115 - (59*1)

= - 115-59 = - 174 mV...!!!