To produce and control energy for all the functions of the cell. Various enzymes and co-enzymes for respiration are obtained from mitochondria. Different stages of respiration such as Krebs cycle , electron transport system , oxidative phosphorylation etc. are performed inside the mitochondria. Mitochondria ensure controlled release of energy. Some participate in the production of DNA and RNA . Mitochondria help in the metabolism of affection. By converting ADP to ATP , it creates high energy bonds and stores them in its body. The mitochondria are called the cell of energy because they provide energy for all the biological functions of the cell.