Question

A 5-year-old girl was washing her doll with shampoo containing a chemical Rotenone. Her mother notices her in an unconscious state. Which of the following complex is inhibited by the above-mentioned chemical?

• A. NADH Dehydrogenase
• B. Succinate DH
• C. Cytochrome C
• D. Cytochrome oxidase

Hint:

Rotenone inhibits NADH dehydrogenase, disrupting ATP production and leading to cellular dysfunction and toxicity.

Answer 1

The Correct Option is A

In the context of mitochondrial electron transport chain, Rotenone is a well-known inhibitor. To understand its impact, let's analyze the specific role of each complex in the electron transport chain:

1. NADH Dehydrogenase (Complex I): This complex is the first entry point for electrons from NADH. Rotenone inhibits this complex, preventing NADH from donating electrons.
2. Succinate DH (Complex II): This complex oxidizes succinate to fumarate, facilitating electron transfer from FADH₂.
3. Cytochrome C: This is a small protein that transfers electrons between Complexes III and IV.
4. Cytochrome oxidase (Complex IV): This complex transfers electrons to oxygen, the final electron acceptor, reducing it to water.

Given that Rotenone specifically inhibits the transfer of electrons from NADH to the ubiquinone in Complex I, the inhibited complex is NADH Dehydrogenase.