Energy Source
Such ion pumps can use energy from a variety of sources, including ATP or the concentration gradient of another ion (sometimes called an "ion exchanger"). Symporters transport anions down their concentration gradient to fuel the transport of another type of ion in the same direction, while antiporters also use the concentration gradient in this same manner but transport in the opposite direction. In contrast, uniporters transport a single ion down its concentration gradient. In all of these cases, there is at least one driving ion that travels down its concentration gradient, thereby providing the energy of the system. Ions that are moved up their concentration gradients are called the driven ion. For a more detailed description of one particular kind of ion pump, see Na+/K+-ATPase.
Read more about this topic: Ion Transporter
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