Question

ATP synthesis occurs on the
A) Outer membrane of mitochondria
B) Inner membrane of mitochondria
C) Matrix
D) None of the above

Answer 1

Hint:ATP stands for adenosine triphosphate. It is the energy carrying molecule found in the cells of all the living beings. ATP captures chemical energy which is obtained from the breakdown of the food molecules and releases this energy as a fuel for other cellular processes.

Complete answer:
ATP synthesis occurs in the mitochondria of the cell by the process of Electron transport chain. Mitochondria is a cell organelle which has 1 outer membrane and 1 inner membrane. The outer membrane is in continuous form and allows the passage of most small molecules and ions. The inner membrane is folded to form a cristae.The inner membrane is a highly selective membrane, it does not allow the passage of all the small molecules and ions.ATP synthesis takes place on the inner membrane of mitochondria by the enzyme ATP synthase. ATP is synthesized by using ADP (adenosine diphosphate) and inorganic phosphate (Pi). It is synthesized by the process of oxidative phosphorylation.

Process of ATP synthesis:
During the transfer of the hydrogen atoms to the oxygen, protons are pumped across the cristae from the inside of the mitochondria to the outside of the mitochondria. As a result an electric potential gradient generated (and in mitochondria a small pH gradient generated) across the membrane which converts chemical energy in the substrate into chemical energy. Now the ATP synthase binds to the ADP and Pi molecules, then the protons that formed outside the mitochondria moves back into the mitochondria with the help of the enzyme. And the energy released is used to convert ADP and PI to ATP. Now the electrical energy is converted into chemical energy. Therefore, ATP synthesis occurs on the inner membrane of mitochondria.

Hence, the correct answer is option ‘B’ i.e, Inner membrane of mitochondria.

Note: In plants, the ATP synthesis do not take place in the Mitochondria. It takes place in the membrane bounded closed sacs called thylakoids that are arranged in the form of stacks and called as grana of chloroplast.