Question

In a polarised state of nerve membrane, sodium-potassium exchange pump actively restores the ions on their appropriate side because ________ against concentration electrochemical gradient.

• A. $Na^+$ is forced out and $K^+$ is forced inside the membrane
• B. both $Na^+$ and $K^+$ are forced out equally
• C. both $Na^+$ and $K^+$ ions are forced inside
• D. $K^+$ is forced out and $Na^+$ is forced inside the membrane

Hint:

Na-K pump rule: 3 Na$^+$ out, 2 K$^+$ in — essential for maintaining resting membrane potential.

Answer 1

The Correct Option is A

Concept:
The sodium-potassium pump (Na$^+$/K$^+$ ATPase) is an active transport mechanism that maintains the resting membrane potential by moving ions against their concentration gradients.

Step 1: Understand ion movement. The pump actively transports:
• 3 Na$^+$ ions out of the cell
• 2 K$^+$ ions into the cell This occurs against their electrochemical gradients using ATP.

Step 2: Analyze the given options.
• (A) Na$^+$ is forced out and K$^+$ is forced inside → Correct \checkmark
• (B) Both ions forced out equally → Incorrect $\times$
• (C) Both ions forced inside → Incorrect $\times$
• (D) Opposite movement → Incorrect $\times$

Step 3: Conclusion. Thus, the correct statement is: \[ \text{Na}^+ \text{ is pumped out and } \text{K}^+ \text{ is pumped into the cell} \]