What is the function of the sodium-potassium pump?

• A. Pump K+ out while pumping Na+ in
• B. Pump 2 Na+ in while pumping 3 K+ out
• C. Pump 3 Na+ out while pumping 2 K+ in
• D. Regulate calcium levels in cells

Answer: (C)

The sodium-potassium pump is a critical membrane transport protein that plays an essential role in maintaining the electrochemical gradient across the plasma membrane of cells. It functions by actively transporting sodium (Na+) ions out of the cell while bringing potassium (K+) ions into the cell. Specifically, the pump moves three sodium ions out of the cell for every two potassium ions it brings in. This activity is necessary for several reasons: it helps to maintain the appropriate concentration of Na+ and K+ within the cell and contributes to the overall membrane potential, which is crucial for nerve impulse transmission and muscle contraction.

The movement of three sodium ions into the extracellular space creates a net positive charge outside the cell, while the transport of two potassium ions into the cell helps to offset this charge, maintaining the negative interior of the cell. Overall, the sodium-potassium pump is vital for cellular function, influencing factors such as osmotic balance and cell volume.

The option that describes the pump's function accurately conveys this mechanism, emphasizing the correct ratio of sodium being transported out compared to potassium being transported in.