Energy Production and Metabolism — MCQs

Q: Inhibitor of F0F1 ATPase in the electron transport chain is

Oligomycin A. ***Oligomycin A*** - **Oligomycin A** directly binds to the **F0 subunit** of the F0F1 ATPase (ATP synthase), blocking the flow of protons through the channel - This inhibition prevents the rotation of the **F1 subunit** and thus stops the synthesis of ATP, effectively uncoupling electron transport from ATP production - It is the **classic inhibitor** used to study oxidative phosphorylation *Incorrect: Antimycin A* - **Antimycin A** inhibits the electron transport chain by blocking electron transfer from **cytochrome b** to **cytochrome c1** in **Complex III** - It does not directly target the F0F1 ATPase, but acts upstream in the chain, thereby reducing the proton gradient necessary for ATP synthesis *Incorrect: 2,4-Dinitrophenol* - **2,4-Dinitrophenol (DNP)** is an **uncoupler**, not an inhibitor, that dissipates the proton gradient across the inner mitochondrial membrane - It creates a shunt for protons, allowing them to flow back into the mitochondrial matrix **without passing through the F0F1 ATPase** - This prevents ATP synthesis but allows electron transport to continue, generating heat instead *Incorrect: Barbiturates* - **Barbiturates** (e.g., amytal) primarily act as inhibitors of **Complex I (NADH dehydrogenase)** in the electron transport chain - By blocking electron flow at Complex I, they prevent the reduction of ubiquinone and subsequent steps in the chain, thereby indirectly affecting ATP production

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