The biological function of ATP (adenosine triphosphate) is to serve as the primary energy carrier in cells. ATP stores and transports chemical energy within cells, facilitating numerous biochemical reactions necessary for life. When ATP is hydrolyzed, it releases energy that powers cellular processes, including muscle contraction, nerve impulse propagation, and biosynthesis of macromolecules. ATP is crucial for metabolism and energy transfer in all living organisms, making it a fundamental molecule in cellular physiology.