What describes the process where the diffusion of one substance drives the transport of another against its concentration gradient?

Cotransport, also known as secondary active transport, describes the process where the diffusion of one substance facilitates the transport of another substance against its concentration gradient. This mechanism relies on the energy derived from the movement of one molecule down its concentration gradient to move another molecule up its gradient.

In cotransport, there are typically two types: symport and antiport. In symport, both substances move in the same direction across the membrane, while in antiport, they move in opposite directions. This is essential in many biological processes, such as nutrient uptake and the maintenance of ion gradients across cell membranes.

Facilitated diffusion, on the other hand, refers to the passive movement of molecules across a membrane via specific transport proteins without the input of energy. Passive transport is a broader category that includes any movement of substances down their concentration gradient without energy input. Endocytosis involves the engulfing of substances into a cell via membrane invagination, which is also distinct from cotransport.