What do cells use for energy?

The only form of energy that cells can use is adenosine triphosphate or ATP. ATP is a high-energy molecule containing three phosphate groups. It stores chemical energy in the bonds that hold it together. The third phosphate group of ATP is attached to the other two phosphate groups with a very high energy bond. 

Cells are unable to derive energy directly from food molecules. Instead, they break down glucose and convert it into energy in the form of ATP in a process known as cellular respiration. Energy is stored when an ATP molecule is formed. When the third phosphate group is cleaved away from the molecule, ATP gets converted to ADP (adenosine diphosphate). The breaking of the third phosphate group releases a large amount of energy that is made available to the cells to perform essential tasks.