How does the proton gradient facilitate ATP synthesis by ATP synthase during chemiosmosis?

• A. The proton gradient allows ATP synthase to transport ATP across the mitochondrial membrane.
• B. The proton gradient directly provides the energy needed for ATP synthase to convert ADP to ATP.
• C. The proton gradient causes ATP synthase to release ATP from the mitochondrial matrix.
• D. The proton gradient inhibits ATP synthase activity, preventing ATP production.

Answer: (B)

Verified step by step guidance

1. Understand the concept of chemiosmosis: Chemiosmosis is the movement of ions across a selectively permeable membrane, down their electrochemical gradient. In mitochondria, this process is crucial for ATP production during cellular respiration.
2. Identify the role of the proton gradient: The proton gradient is established across the inner mitochondrial membrane by the electron transport chain. As electrons move through the chain, protons (H+) are pumped from the mitochondrial matrix into the intermembrane space, creating a high concentration of protons outside the matrix.
3. Recognize the function of ATP synthase: ATP synthase is an enzyme located in the inner mitochondrial membrane. It uses the energy from the flow of protons back into the mitochondrial matrix to catalyze the conversion of ADP and inorganic phosphate (Pi) into ATP.
4. Explain how the proton gradient facilitates ATP synthesis: The proton gradient creates a potential energy difference across the membrane. As protons flow back into the matrix through ATP synthase, this energy is harnessed to drive the synthesis of ATP from ADP and Pi.
5. Clarify the misconception: The proton gradient does not transport ATP across the membrane nor inhibit ATP synthase. Instead, it provides the necessary energy for ATP synthase to function, enabling the production of ATP.