Question

If a neuronal plasma membrane is permeable only to sodium ions and the concentration of sodium ions on one side of the membrane is the same as that on the other side, then which of the following statements best characterizes the resting membrane potential for that cell?

a) The resting membrane potential is established due to sodium ion concentration gradients.
b) The resting membrane potential is established due to the selective permeability of sodium ions.
c) The resting membrane potential is zero since sodium ion concentration is the same on both sides.
d) The resting membrane potential is determined by the active transport of sodium ions.

Answer 1

The resting membrane potential would be zero in the described scenario where the membrane is only permeable to sodium ions and the concentrations of sodium are the same on both sides.

Step-by-step explanation:

If the neuronal plasma membrane is permeable only to sodium ions (Na+) and the concentration of Na+ is the same on both sides, then the resting membrane potential would best be characterized by option c) i.e., 'The resting membrane potential is zero since sodium ion concentration is the same on both sides.'

The resting membrane potential of a neuron is typically around -70mV and is primarily established by the gradient of ions across the cell membrane and their selective permeability. The potassium ions (K+) have a greater influence on the resting membrane potential due to the cell being more permeable to K+ than Na+. Under usual circumstances, the sodium-potassium pump plays a role in maintaining the ion gradient, by expelling more Na+ than it brings in K+, using ATP in the process.

In this hypothetical scenario, since the Na+ concentrations are equal across the membrane and assuming no other ions are involved and the membrane is only permeable to Na+, there would be no potential difference across the membrane, resulting in a resting membrane potential of 0mV.