Here's why:

* Cellular Respiration: Mitochondria are the powerhouses of the cell. They are the sites of cellular respiration, a process that breaks down glucose (a sugar) in the presence of oxygen to produce ATP (adenosine triphosphate), the primary energy currency of cells.

* ATP Production: Through a series of chemical reactions, mitochondria convert the chemical energy stored in glucose into a usable form of energy in the form of ATP.

Let me know if you'd like to learn more about cellular respiration!