Which of the following best describes the sodium-potassium ATPase?

• A. A ligand-gated ion channel
• B. A peripheral membrane protein
• C. A secondary active transporter
• D. A primary active transport protein

Answer: (D)

Verified step by step guidance

1. Understand the role of the sodium-potassium ATPase: It is a membrane protein responsible for maintaining the electrochemical gradient across the plasma membrane by actively transporting sodium (Na⁺) and potassium (K⁺) ions against their concentration gradients.
2. Identify the type of transport: Sodium-potassium ATPase uses energy derived from ATP hydrolysis to move ions against their gradients. This is a hallmark of primary active transport, as it directly uses ATP as an energy source.
3. Eliminate incorrect options: A ligand-gated ion channel allows ions to pass through the membrane in response to a ligand binding, but it does not actively transport ions. Sodium-potassium ATPase is not a peripheral membrane protein because it spans the membrane (integral protein). It is also not a secondary active transporter, as secondary active transport relies on the energy from an existing gradient rather than directly using ATP.
4. Correlate the function with the correct classification: Since sodium-potassium ATPase directly uses ATP to pump ions, it is classified as a primary active transport protein.
5. Conclude: The correct description of the sodium-potassium ATPase is 'A primary active transport protein,' as it directly uses ATP to move ions against their concentration gradients.