I agree - it is respiration. Respiration may be loosely defined as the breakdown of foods to yield energy.
Anaerobic respiration involves a limited set of chemical reactions, known as Glycolysis, without the presence of oxygen.
Aerobic respiration involves Kreb's Cycle and the Electron transport chain as well as glycolysis, and is dependent upon oxygen. Aerobic respiration breaks the food molecules down into smaller fragments and yields more energy. It is found in all living organisms other than a few very primitive bacteria