Flexi Says: ATP supplies the energy for most active transport. One way ATP powers active transport is by transferring a phosphate group directly to a carrier protein. This may cause the carrier protein to change its conformation, which moves the molecule or ion to the other side of the membrane. An example of this type of active transport system is the sodium-potassium pump, or Na+/K+-ATPase, a transmembrane ATPase, an integral membrane protein that exchanges sodium ions for potassium ions across the plasma membrane of animal cells. The sodium-potassium pump is found in the plasma membrane of almost every human cell and is common to all cellular life. It helps maintain resting potential, especially in neurons following a nerve impulse, and regulates cellular volume.