The process our cells use to take in food and oxygen is called cellular respiration. Cellular respiration is a set of chemical reactions cells use to change the food we eat, the water we drink, and oxygen from the air we breathe into forms the cell can use as energy.Cellular respiration is the process by which the chemical energy of "food" molecules is released and partially captured in the form of ATP. Carbohydrates, fats, and proteins can all be used as fuels in cellular respiration, but glucose is most commonly used as an example to examine the reactions and pathways involved.