Question

The chemiosmotic coupling hypothesis of oxidative phosphorylation proposes that adenosine triphosphate (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 toward adenosine diphosphate (ADP)

Answer 1

Answer: (C)

The chemiosmotic theory postulated by the British biochemist Peter Mitchell ( $1920-22$ ) to explain the formation of ATP in the mitochondrial electron transport chain. As electrons are transferred along with the electron carrier system in the inner mitochondrial membrane, hydrogen ions (protons) are actively transported into the space between the inner and outer mitochondrial membranes, thus containing a higher concentration of protons than the matrix. This creates an electrochemical gradient across the inner membrane, through which protons move back into the matrix.