What is a key characteristic of active transport in cellular processes?

Active transport is characterized by its ability to move substances against their concentration gradient, which is a fundamental aspect of the process. This means that active transport can take molecules from an area of lower concentration to an area of higher concentration, a movement that opposes the natural flow dictated by diffusion. This process is crucial for maintaining concentrations of ions and other substances necessary for various cellular functions, such as nutrient uptake and maintaining the electrochemical gradients across membranes.

This mechanism relies on energy input, typically from ATP, to facilitate the movement of molecules, differentiating it significantly from passive transport mechanisms that occur spontaneously without energy expenditure. The capacity to move substances against their concentration gradient enables cells to maintain homeostasis and regulate vital processes efficiently.