Question

In the resting state of the neutral membrane, diffusion due to concentration gradients, if allowed, would drive.

• A. $K^{+}$ into the cell
• B. $K^{+}$ and $N{a}^{+}$ out of the cells
• C. $N{a}^{+}$ into the cells
• D. $N{a}^{+}$ out of the cell

Answer 1

Answer: (A)

$K^{+}$ into the cell

The cytoplasm inside the axon of a resting nerve fibre has a high concentration of $K^{+}$ and a low concentration of $N{a}^{+}$. It is in contrast to the fluid present outside the axon. So, if diffusion takes place through a concentration gradient.

In other words, the concentration gradients across the resting membrane are maintained by the active transport of ions by the sodium-potassium pump which transports $3N{a}^{+}$ outward for $2K^{+}$ into the cell.

Hence, option A is correct.