An electric motor turns a belt that powers a pump. If this system is compared to the chemical reactions of the cell, which part represents ATP

The electricity on which the motor runs represents ATP.

ATP, adenosine triphosphate, is the energy currency of the cell. The energy released during the process of respiration is stored in the ATP molecule, and the ATP is stored within cells. Whenever the cell requires energy for any function, it simply hydrolyzes the ATP molecule, breaking a phosphate group off and releasing energy in the process.