: The main function of the mitochondria is to assist the organism in respiration. The four stages of respiration, glycolysis , the formation of acetylcholine , the Krebs cycle, and the electron flow system, the second and most important of which are the reactions of the Krebs cycle. Since all the enzymes involved in the Krebs cycle are present in it, these reactions take place in the mitochondria. The Krebs cycle produces the most energy. This is why mitochondria are called the power house of the cell.