Here's why:

* Energy Production: Mitochondria are responsible for the process of cellular respiration, which breaks down glucose (sugar) and converts it into ATP (adenosine triphosphate). ATP is the primary energy currency of cells, powering all cellular activities.

* Cellular Respiration: This process involves a series of chemical reactions that occur in the mitochondria. They utilize oxygen and produce carbon dioxide as byproducts.

So, mitochondria are crucial for supplying the energy that cells need to function.