A sodium-potassium pump is an enzyme found in the membrane of most cells. It is a way to transport sodium and potassium ions across the cell membrane, against their concentration gradient (low to high concentration). The mechanism of a sodium-potassium pump is as follows:

1. 3 Sodium ions bind the the pump.
2. ATP binds to the pump and is hydrolyzed.
3. The pump is phosphorylated which leads to a conformational change in the pump.
4. The 3 Sodium ions are released into the extracellular region.
5. 2 Potassium ions bind to the pump.
6. Dephosphorylation of the pump changes the pump to its original conformation.
7. The 2 Potassium ions are released into the cell.