Question

the sodium-potassium pump helps maintain the concentration gradients for sodium and potassium ions across the plasma membrane. select the true statement regarding the sodium-potassium pump. for each molecule of atp used, the pump moves two negatively charged sodium ions into the cell. for each molecule of atp used, the pump moves three positively charged sodium ions out of the cell. for each molecule of atp used, the pump moves three positively charged potassium ions out of the cell. for each molecule of atp used, the pump moves two negatively charged potassium ions out of the cell. i dont know yet

Explanation:

The sodium - potassium pump is an active transport mechanism. For each molecule of ATP hydrolyzed, the sodium - potassium pump moves 3 positively charged sodium ions out of the cell and 2 positively charged potassium ions into the cell.

• Option 1: Sodium ions are positively charged and the pump moves them out of the cell, not into, so this is wrong.
• Option 2: This matches the function of the sodium - potassium pump (3 Na⁺ out per ATP used), so this is correct.
• Option 3: The pump moves potassium ions into the cell, not out, so this is wrong.
• Option 4: Potassium ions are positively charged and the pump moves them into the cell, not out, so this is wrong.

Answer:

B. For each molecule of ATP used, the pump moves three positively charged sodium ions out of the cell. (Here we assume the second option is labeled as B, following the common multiple - choice labeling convention. If the original options had different labels, adjust accordingly based on the actual labeling in the problem. But from the content, the second option is the correct one.)