Hi, Sade. Mitochondria are sometimes described as "cellular power plants" because they generate most of the cell's supply of adenosine triphosphate (ATP), used as a source of chemical energy. In addition to supplying cellular energy, mitochondria are involved in other tasks such as signaling, cellular differentiation, cell death, as well as the control of the cell cycle and cell growth
You should really do some research on your own instead of relying on many people to give you the answer. You will learn something that you will need to know in the future, by doing so. Don't think I'm being mean.