The molecule that serves as the main energy carrier in cells is adenosine triphosphate (ATP). ATP consists of adenine, ribose, and three phosphate groups, and it functions as a universal energy currency for biological processes. When ATP is hydrolyzed, it releases energy that powers various cellular activities, including muscle contraction, protein synthesis, and active transport. The continuous regeneration of ATP from adenosine diphosphate (ADP) and inorganic phosphate makes it a crucial component in metabolism, ensuring that cells have a consistent supply of energy.