Antiporter

An antiporter is an integral membrane protein that is involved in active transport of two or more different molecules or ions across a phospholipid membrane such as the plasma membrane in opposite directions.

In primary active transport, all molecules are moved against their concentration gradients, fuelled by ATP. In secondary active transport, one molecule moves along its electrochemical gradient, allowing the other to move against its electrochemical gradient.

It should be noted that although two or more types of molecule are transported, there may be several molecules transported of each type.

Examples
3Na+/2K+ ATPase is found in many cell types, notably in the neurites of neurones. Its purpose is to maintain the resting membrane potential.