The sodium-potassium pump carries out a form of active transport and pumps ions against their electrochemical gradients. ATP is the external energy source required for the process to occur. When ATP binds to the pump, ATP phosphorylates the pump and alters its shape, forming an opening towards the exterior of the cell. The enzyme sodium-potassium-ATPase splits ATP into ADP and phosphate. The energy released from phosphorylation fuels the transport mechanism of the pump.