Which of the following primarily regulates sodium and potassium levels in cells?

The regulation of sodium and potassium levels within cells is primarily accomplished through primary active transport, specifically via the sodium-potassium pump (Na+/K+ ATPase). This pump actively transports sodium ions out of the cell while bringing potassium ions into the cell, maintaining the essential electrochemical gradient across the cell membrane.

This mechanism requires energy, specifically the hydrolysis of ATP, to move ions against their concentration gradients. Sodium is typically more concentrated outside the cell, while potassium is more concentrated inside. By using active transport, the sodium-potassium pump effectively establishes a resting membrane potential, which is crucial for various cellular functions, including action potentials in neurons and muscle cells.

Understanding the role of primary active transport in regulating these ions helps elucidate the critical balance necessary for maintaining cellular homeostasis and function.