What is a contransport?

Answer 1

Transport across membranes can be fueled not only by ATP, but by the energy stored in ion gradients. In such cases, the free energy released during the transport of ions down an electrochemical gradient is used to pump other ions or molecules up their electrochemical gradient. This process is called cotransport because one carrier protein mediates the transport of both species. Some cotransporters carry both solutes in the same direction (symport), while others transport one solute into the cell and the other out of the cell (antiport).

Answer 2

A cotransporter is a protein that plays a role in transporting two or more different molecules or ions across a cell membrane simultaneously. This process is often coupled with the movement of another molecule or ion down its concentration gradient to provide the energy needed for transport.