The molecule ATP (adenosine triphosphate) is known as the energy currency of the cell because it stores and transfers energy required for various cellular processes. ATP releases energy upon hydrolysis of its high-energy phosphate bonds, which powers metabolic activities such as muscle contraction, nerve impulse propagation, and biochemical synthesis. Unlike DNA or RNA, ATP's primary role is energy transfer, not information storage. Its rapid regeneration from ADP and inorganic phosphate ensures continuous energy supply to sustain vital cellular functions, making it indispensable in clinical and surgical contexts where tissue metabolism and repair are critical.

Reference: Principles of Biochemistry, Lehninger, 7th Edition.