Fig., (A) shows the cell organelle mitochondria. The mitochondria are bounded by two membranes, i.e., outer membrane and inner membrane. Mitochondria are referred as “powerhouse” of the cell as they produce 95% of ATP. This energy is produced during the break down of food molecules which involve glycolysis, oxidative decarboxylation and oxidative phosphorylation (Kreb’s cycle and respiratory chain).