Here's why:

* Cellular Respiration: This process breaks down glucose (a sugar) in the presence of oxygen to produce ATP (adenosine triphosphate), the primary energy currency of cells.

* ATP Production: The breakdown of a single glucose molecule can generate a significant amount of ATP.

* Energy Release: This energy stored in ATP is then used to power various cellular processes, like muscle contraction, active transport, and biosynthesis.

While the amount of energy released from a single glucose molecule might seem small, the sheer number of glucose molecules that are constantly being broken down in a living organism results in a significant energy output.