In biology, an ion transporter, also called an ion pump, is a transmembrane protein that moves ions across a plasma membrane against their concentration gradient, in contrast to ion channels, where ions go through passive transport. These primary transporters are enzymes that convert energy from various sources, including ATP, sunlight, and other redox reactions, to potential energy stored in an electrochemical gradient. This energy is then used by secondary transporters, including ion carriers and ion channels, to drive vital cellular processes, such as ATP synthesis.