Question

At rest, a human neuron has a membrane potential of −70mV. Based on this image, which of the following statements best explains how the negative membrane potential is generated?

The lipid bilayer is highly permeable to potassium ions but semipermeable to sodium ions, allowing a greater outflow of positive potassium ions than inflow of negative sodium ions.
The potassium channels transfer four potassium ions out while the sodium channels transfer two sodium ions in, resulting in a net outflow of positive potassium ions.
The presence of more potassium channels than sodium channels in the membrane results in a net outflow of positive potassium ions.
The sodium-potassium pumps and sodium channels require ATP to transfer ions, but the potassium channels transfer ions through facilitated diffusion, resulting in a net outflow of potassium ions.

Answer 1

The negative resting membrane potential of a neuron is primarily a result of the selective permeability of the membrane to potassium ions over sodium ions, facilitated by the greater number of potassium leakage channels and the action of the sodium-potassium pump.

Step-by-step explanation:

The negative membrane potential of a human neuron at rest, typically measured at -70mV, is primarily generated due to the selective permeability of the neuron's membrane to certain ions. The most significant contribution to this resting membrane potential is the movement of potassium ions (K+) out of the cell, which occurs more readily than the movement of sodium ions (Na+) into the cell because the membrane has more potassium leakage channels than sodium leakage channels. Additionally, the sodium-potassium pump, which actively transports 3 Na+ out of the cell and brings 2 K+ into the cell using ATP, further maintains the difference in ion concentration across the cell membrane.

The correct explanation for the negative membrane potential being created is the combination of the potassium channels allowing more K+ to move out than sodium channels allowing Na+ in, and the action of the sodium-potassium pump which moves more positive ions out than it brings in, thus increasing the negative charge inside relative to the outside. It is important to note that while these processes help establish the resting membrane potential, it is the difference in permeability to K+ compared to Na+ through leakage channels that is the main factor causing the resting negative charge.