Question

The Nernst equilibrium potential for K+ is -90mV and

for Na+ is +60mV. The membrane potential (Vm)
of a cell only permeable to Na+ ions would be
Select one:
a.
-90mV
b.
-75mV
c.
0mV
d.
+60mV

Answer 1

The correct answer is d which is +60mV

Step-by-step explanation:

The Nernst equation gives us the equilibrium potential for an ion based on its concentration gradient and the Faraday constant. The equation is:

ENa+ = (RT/zF) *ln([Na+]out/[Na+]

Where:

ENa+ = Equilibrium potential for Na+

R = Gas constant

T = Temperature (in Kelvin)

z = Valence of the ion (in this case, +1 for Na+)

F = Faraday constant

[Na+]out = Concentration of Na+ outside the cell

[Na+]in = Concentration of Na+ inside the cell

Given that the cell is only permeable to Na+ ions, the concentration of Na+ inside and outside the cell will be the same. Therefore, [Na+]out/[Na+]in = 1.

ENa+ = +60mV, z = +1, and [Na+]out/[Na+]in = 1,

we can rearrange the Nernst equation to solve for Vm:

Vm = ENa+

Vm = +60mV

Therefore, the membrane potential (Vm) of a cell that is only permeable to Na+ ions would be +60mV. The correct answer is d.