The chemical reactions that break down food molecules in cells to release energy are defined as cellular respiration.

Here's a breakdown:

* Cellular respiration is the process by which cells convert chemical energy from food molecules, like glucose, into a form of energy that the cell can use, called ATP (adenosine triphosphate).

* This process involves a series of chemical reactions, primarily occurring in the mitochondria of eukaryotic cells.

* There are three main stages: glycolysis, the Krebs cycle, and oxidative phosphorylation.

Let me know if you'd like a more detailed explanation of each stage!