Respiration is defined as an enzyme mediated process of biological oxidation of food material such as carbohydrate, fat etc. In this process generally there is in take of oxygen and release of CO2 . (aerobic respiration). However, in some cases oxygen is not required (anaerobic respiration). In all cases there is release of considerable amount of energy. Maximum amount of energy is produced during Krebs cycle which takes place in matrix of mitochondria.