The function of the sodium-potassium pump in cells is to maintain the electrochemical gradient across the plasma membrane. This pump actively transports sodium ions (Na+) out of the cell and potassium ions (K+) into the cell, utilizing ATP for energy. This ion exchange is crucial for various physiological processes, including nerve impulse transmission and muscle contraction. By sustaining the appropriate levels of these ions, the sodium-potassium pump plays a vital role in cellular homeostasis and overall cell function.