ATP

Fig. 1: ATP Cycle

To trap energy released from catabolic chemical reactions, the cell uses that released energy to attach a phosphate group onto ADP (adenosine diphosphate) to make ATP (adenosine triphosphate). Thus, energy is trapped and stored in high-energy phosphate bonds. To obtain energy to do cellular work, the cell enzymatically removes the third phosphate from ATP thus releasing the stored energy and forming ADP and phosphate once again.