Question

A muscle cell has an intracellular [Na⁺] of 14 mM and an extracellular [Na⁺ ] of 140 mM. Assuming that 2.3 RT/F = 60 mV, what would the membrane potential be if the muscle cell membrane were permeable only to Na⁺?

1) 80 mV
2) -60 mV
3) 0 mV
4) +60 mV
5) +80 mV

Answer 1

The membrane potential of a muscle cell permeable only to Na+ ions, given the provided concentrations and the simplified Nernst equation, would be +60 mV.

Step-by-step explanation:

To calculate the membrane potential of a muscle cell permeable only to Na+, we can use the Nernst equation. However, in this case, we're given the relationship that 2.3 RT/F equals 60 mV, which simplifies the computation.
The Nernst equation in its simplified form for Na+ is:
ENa = 60 mV * log([Na+] outside / [Na+] inside)
Plugging in the given concentrations, we have:
ENa = 60 mV * log(140 mM / 14 mM)
ENa = 60 mV * log(10)
ENa = 60 mV * 1
ENa = +60 mV
The membrane potential with the given concentrations would be +60 mV.