Which statement about the Na+/K+ pump energy usage is correct?

• A. It is a primary active transporter driven directly by ATP
• B. It is a secondary active transporter driven by ion gradients
• C. It is a passive channel
• D. It transports glucose

Answer: (A)

The key idea here is that the Na+/K+ pump uses energy directly from ATP to move ions against their gradients, making it a primary active transporter. In each cycle, it hydrolyzes one ATP to drive conformational changes that pump three Na+ out of the cell and two K+ into the cell. This direct use of ATP energy, rather than relying on existing ion gradients, is what defines primary active transport. It is not a secondary active transporter, which would harness the energy stored in gradients to move substances; it is not a passive channel, which would allow ions to diffuse down their gradients without energy input. It also does not transport glucose, which is handled by other transporters such as GLUTs (facilitated diffusion) or by cotransporters like SGLT that rely on the Na+ gradient. The pump’s role in maintaining ion gradients is essential for resting membrane potential and cell volume, and that energy demand comes from direct ATP hydrolysis.