Question

The chemiosmotic coupling hypothesis of oxidative phosphorylation proposes that ATP is formed because:

• A. High energy bonds are formed in mitochondrial proteins.
• B. ADP is pumped out of the matrix into the intermembrane space.
• C. A proton gradient forms across the inner membrane.
• D. There is a change in the permeability of the inner mitochondrial membrane towards ADP.

Answer 1

The correct option is C A proton gradient forms across the inner membrane.

The chemiosmotic coupling hypothesis of oxidative phosphorylation proposed by Mitchell, explains the process of ATP formation and states that it is linked to development of a proton gradient across the mitochondrial membrane. ATP synthetase (ATP synthase), required for ATP synthesis, is located in $F_1$ particles present in the inner mitochondrial membrane. It becomes active only when there is high concentration of protons on the $F_0$ side as compared to $F_1$ side. The flow of protons through the $F_0$ channel induces $F_1$ particles to function as ATP synthase releases energy. Energy of proton gradient produces ATP by attaching an inorganic phosphate ($P_i$) to ADP.