Active transport is a mechanism used by cells to move specific molecules or ions across biological membranes against their concentration gradient. Unlike passive transport, which relies solely on the inherent difference in solute concentration and does not require metabolic energy, active transport requires the expenditure of energy, typically derived from the hydrolysis of adenosine triphosphate (ATP). This energy is harnessed by specific membrane proteins, known as pumps or carriers, which bind to the target substance and induce a conformational change to facilitate translocation. This process is crucial for maintaining the necessary electrochemical gradients across cell boundaries, allowing the cell to accumulate substances or expel waste products that would otherwise diffuse out, thereby establishing and maintaining cellular homeostasis.