Which transport mechanism utilizes energy from cotransported ions to move substances against their concentration gradient?

Secondary active transport is a mechanism that utilizes the energy derived from the movement of ions down their concentration gradient to facilitate the transport of other substances against their gradient. This process involves two distinct components: the cotransport of ions, typically sodium or hydrogen ions, which are moving from an area of higher concentration to an area of lower concentration. As these ions flow into the cell, they create an energy gradient that can be harnessed to move another molecule against its own concentration gradient.

For example, in the case of sodium-glucose cotransport, sodium ions are actively pumped out of the cell, creating a gradient. When sodium ion concentration is higher outside than inside the cell, sodium can enter the cell along with glucose, which is then transported against its concentration gradient into the cell. This illustrates how secondary active transport relies on the energy from the cotransport of ions to achieve its function.

In contrast, primary active transport does not involve cotransported ions in the same way; instead, it directly uses ATP to pump ions against their gradients. Passive diffusion involves the movement of substances along their concentration gradient without any energy input. Endocytosis is a process where cells take in substances by engulfing them, which also does not specifically involve the cotrans