In biology, an ion pump is a transmembrane protein that moves ions across a plasma membrane against their concentration gradient. Such ion pumps, sometimes also known as ion transporters, can use energy from a variety of sources, including ATP or the concentration gradient of another ion (sometimes called an "ion exchanger"). For a more detailed description of one particular kind of ion pump, see NaKATPase. Na+/K+-ATPase (also known as the Na+/K+ pump or Na+/K+ exchanger) is an enzyme (EC 3. ...