* Glucose (C6H12O6): This is the primary energy source for the process.

* Oxygen (O2): This is the oxidizing agent, accepting electrons and allowing the breakdown of glucose to release energy.

While these are the primary reactants, cellular respiration also requires other substances like:

* Water (H2O): Used in certain steps of the process.

* ADP (adenosine diphosphate): This is a molecule that gets phosphorylated (gains a phosphate group) to form ATP, the energy currency of the cell.

* Phosphate (Pi): Required for the production of ATP.

It's important to remember that cellular respiration is a complex process with many steps, and different reactants are involved at various stages.