In oxidative phosphorylation, which structure in the inner mitochondrial membrane is directly responsible for synthesizing ATP from ADP and inorganic phosphate?

• A. Cytochrome c oxidase (Complex IV)
• B. Cytochrome $b{c}_1$ complex (Complex III)
• C. NADH dehydrogenase (Complex I)
• D. ATP synthase (Complex V, $F{o}_0–$ F{1}_1$ATPase)$

Answer: (D)

Verified step by step guidance

1. Understand that oxidative phosphorylation occurs in the inner mitochondrial membrane and involves a series of protein complexes that transfer electrons and pump protons to create a proton gradient.
2. Identify the role of each complex: Complex I (NADH dehydrogenase), Complex III (Cytochrome bc1 complex), and Complex IV (Cytochrome c oxidase) are primarily involved in electron transport and proton pumping, not directly in ATP synthesis.
3. Recognize that ATP synthesis requires a specialized enzyme that uses the proton gradient to catalyze the formation of ATP from ADP and inorganic phosphate (Pi).
4. Recall that ATP synthase (also known as Complex V or F0–F1 ATPase) is the enzyme embedded in the inner mitochondrial membrane responsible for this process, harnessing the proton motive force to drive ATP production.
5. Conclude that among the given options, ATP synthase (Complex V) is directly responsible for synthesizing ATP during oxidative phosphorylation.