Glucose and oxygen play the role of the reactants in cellular respiration. We breathe in oxygen and our bodies use glucose (sugar) to make energy. Energy is then stored as ATP and CO2.
Cellular respiration is the process by which the chemical energy of "food" molecules is released and partially captured in the form of ATP. Cellular respiration takes place in the mitochondria of the cell. Carbohydrates, fats, and proteins can all be used as fuels in cellular respiration, but glucose is most commonly used to provide energy to the organism.
