What term refers to the energy-requiring process that moves material against a concentration gradient?

The term that refers to the energy-requiring process that moves material against a concentration gradient is active transport. This process is essential because it allows cells to maintain concentrations of certain ions and molecules that differ from those in their environment, which is critical for various cellular functions.

Active transport involves the use of energy, typically from adenosine triphosphate (ATP), to move substances against their concentration gradient. This means that molecules are transported from areas of lower concentration to areas of higher concentration. For instance, the sodium-potassium pump is a well-known example of active transport, where sodium ions are expelled from a cell while potassium ions are brought in, both against their respective concentration gradients.

In contrast, osmosis is the passive movement of water molecules through a semi-permeable membrane from an area of lower solute concentration to an area of higher solute concentration. Facilitated diffusion is another passive process that involves the movement of molecules across a membrane through specific transport proteins, allowing substances to flow down their concentration gradient without the expenditure of energy. Simple diffusion, similarly, is the process of particles moving from an area of higher concentration to an area of lower concentration without any energy input. Understanding these distinctions clarifies why active transport is the correct answer, as