Cell respiration is the series of enzyme-mediated chemical reactions that break down substrate molecules such as glucose into carbon dioxide and water. This releases chemical energy used to build up ATP (adenosine triphosphate) that can then be used for all the cells energy needs.

Cell respiration occurs in four stages:

1. Glycolysis in the cell cytoplasm

2. Link reaction in the mitochondrial matrix

3. Krebs cycle in the mitochondrial matrix

4. Electron transport chain on the inner mitochondrial membrane (cristae)