What is the role of the sodium-potassium pump?

What is the role of the sodium-potassium pump?

• A. It moves Na+ into the cell and K+ out.
• B. It transports 3 Na+ out and 2 K+ in, maintaining ionic gradients and the negative intracellular potential.
• C. It allows diffusion of ions down their gradient without ATP.
• D. It pumps Na+ out and K+ in, using ATP.

Answer: (B)

The Na+/K+ pump is an active transporter that uses ATP to move ions against their gradients, keeping the cell’s interior ion balance and membrane potential stable. It moves three sodium ions out of the cell and two potassium ions in for each cycle. This exact 3:2 exchange creates a net outward positive current, which helps maintain the negative resting membrane potential inside the cell. Keeping intracellular Na+ low also supports other cellular processes that rely on ion gradients, such as secondary active transport and volume regulation. So, the action described—3 Na+ out and 2 K+ in, maintaining ionic gradients and the negative intracellular potential—best captures how this pump functions. The other descriptions either reverse the directions, describe passive diffusion, or omit the specific stoichiometry and energy dependence.

The Na+/K+ pump is an active transporter that uses ATP to move ions against their gradients, keeping the cell’s interior ion balance and membrane potential stable. It moves three sodium ions out of the cell and two potassium ions in for each cycle. This exact 3:2 exchange creates a net outward positive current, which helps maintain the negative resting membrane potential inside the cell. Keeping intracellular Na+ low also supports other cellular processes that rely on ion gradients, such as secondary active transport and volume regulation. So, the action described—3 Na+ out and 2 K+ in, maintaining ionic gradients and the negative intracellular potential—best captures how this pump functions. The other descriptions either reverse the directions, describe passive diffusion, or omit the specific stoichiometry and energy dependence.