This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: ETC, Subject name: Biochemistry
Barbiturates act on which step of mitochondrial respiratory chain: 
Select and explain. 
A. Complex I to Co-enzyme Q, B. Coenzyme Q to Complex III, C. Complex II to Coenzyme Q, D. Cytochrome C to Complex IV
A: Complex I to Co-enzyme Q
Answer: A: Complex I to Co-enzyme Q 
Explanation: option a : Barbiturates such as amobarbital inhibit electron transpo Complex I by blocking the transfer from complex I to Coenzyme Complexes Inhibitors of ETC Complex I (NADH-CoQ reductase/NADH dehydrogenase) Rotenone, Phenobarbitone, Amobarbital, Piericidin A Complex II (Succinate CoQ reductase) Malonate (3C) Carboxin (Fungicide) TTFA (Trienoyl Tri Fluoro Acetone) Complex III (Cyt c reductase) Phenoformin Antimycin A BAL (British Anti Lewisite) or Dimercaprol) Complex IV (Cyt c oxidase) CO Cyanide (CN), H2S, Sodium Azide Uncouplers of ETC: Dinitrophenol, Thermogenin ADP to ATP conversion is inhibited by: Oligomycin ADP to ATP transfer is inhibited by: Atractyloside