Transcellular transport, animation. Solutes can be transported across a cell's membrane in several ways. Here are three examples of transmembrane proteins that transport ions and molecules into or out of a cell. At top is a symporter, which catalyses the movement of a molecule against its concentration gradient, driven by the movement of one or more ions down an electrochemical gradient. At bottom left is a uniporter, which transports a single type of molecule down its concentration gradient. At bottom right is an antiporter channel, which transports two or more different solutes across the cell membrane in opposite directions, driven by the energy released by the hydrolysis of ATP (adenosine triphosphate) into ADP (adenosine diphosphate) and inorganic phosphate (Pi).
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