1) Mitochondria are known as power houses of cell. The mitochondria are the double membrane structure that can grow, fuse with one another and capable of dividing. During the replication of mitochondrial DNA the mitochondria become double in size. They are oval in structure with plain outer membrane and the inner membrane exhibits folding known as cristae. The inner membrane encloses mitochondrial matrix. The matrix contains the DNA and enzymes involved in citric acid cycle or Krebs cycle. The cristae lodge the enzymes required in the electron transport chain to carry out the process of oxidative phosphorylation. The energy is produced through a series of steps in which the electrons are transported and the protons are pumped out of the matrix into the inner space between the two membranes creating the electron potential gradient across the membranes. The protons flow back to the matrix through an enzyme complex known as ATP synthase that is found in cristae and utilizes the energy produced by the flow of protons to phosphorylate the ADP forming the ATP. 2) uncoupler or uncoupling protein (UCP) is a mitochondrial protein located in the inner membrane. These are involved in inhibition of the coupling between the electron transport and phosphorylation reactions. As a result, synthesis of ATP is inhibited without affecting the respiratory chain and ATP synthase (H+ -ATPase). 3) Under availability of oxygen the cell is more efficient in the energy. Under anaerobic conditions the process of glucose breakdown cannot proceed further after glycolysis. The glycolysis takes place in the cytosol producing 2 ATP molecules per each glucose molecule. In presence of oxygen or under aerobic conditions the process of glycolysis further proceeds for mitochondrial processing including the citric acid cycle and the electron transport system. This process supplies enough energy to produce 30 more ATP molecules comprising to the total yield of 32 ATP molecules per glucose molecule at the end of aerobic respiration. Thus, the ATP molecules produced are 2 by glycolysis 2 by citric acid cycle and 28 by oxidative phosphorylation. Hence, aerobic respiration is an energy efficient process than anaerobic respiration. Solution 1) Mitochondria are known as power houses of cell. The mitochondria are the double membrane structure that can grow, fuse with one another and capable of dividing. During the replication of mitochondrial DNA the mitochondria become double in size. They are oval in structure with plain outer membrane and the inner membrane exhibits folding known as cristae. The inner membrane encloses mitochondrial matrix. The matrix contains the DNA and enzymes involved in citric acid cycle or Krebs cycle. The cristae lodge the enzymes required in the electron transport chain to carry out the process of oxidative phosphorylation. The energy is produced through a series of steps in which the electrons are transported and the protons are pumped out of the matrix into .