Chemiosmotic creation of ATP is driven by:

• A. Phosphate transfer through the plasma membrane.
• B. Potential energy of the H⁺ concentration gradient created by the electron transport chain.
• C. Substrate-level phosphorylation in the mitochondrial matrix.
• D. Large quantities of ADP in the mitochondrial matrix.

Answer: (B)

Verified step by step guidance

1. Understand the concept of chemiosmosis: Chemiosmosis is the process by which ATP is produced in the mitochondria. It involves the movement of hydrogen ions (H+) across a membrane, creating a gradient that drives ATP synthesis.
2. Identify the role of the electron transport chain: The electron transport chain is responsible for creating the H+ concentration gradient. As electrons are passed along the chain, energy is used to pump H+ ions from the mitochondrial matrix into the intermembrane space.
3. Recognize the importance of the H+ concentration gradient: The potential energy stored in the H+ concentration gradient is crucial for ATP synthesis. This gradient represents a form of stored energy that can be harnessed to produce ATP.
4. Explain how ATP is synthesized: ATP synthase, an enzyme located in the mitochondrial membrane, uses the energy from the flow of H+ ions back into the matrix to catalyze the conversion of ADP and inorganic phosphate into ATP.
5. Differentiate chemiosmosis from substrate-level phosphorylation: Substrate-level phosphorylation is a different mechanism of ATP production that occurs directly in the mitochondrial matrix during glycolysis and the Krebs cycle, independent of the electron transport chain.