38. Match the compounds in Group I with the correct entries in Group II.
Group I Group II
P) Cyanide 1) K+ ionophore
Q) Antimycin A 2) Electron transfer from cytochrome b to cytochrome c1
R) Valinomycin 3) F1 subunit of ATP synthase
S) Aurovertin 4) Cytochrome oxidase
5) Adenine nucleotide translocase
(A) P-5, Q-2, R-3, S-1
(B) P-5, Q-2, R-1, S-3
(C) P-4, Q-2, R-1, S-3
(D) P-4, Q-5, R-3, S-1
Cyanide, Antimycin A, Valinomycin, and Aurovertin are key inhibitors of mitochondrial electron transport chain (ETC) and ATP synthesis processes. The correct matching is option (C): P-4, Q-2, R-1, S-3, as it accurately pairs each compound with its specific target based on biochemical mechanisms.
Compound Functions
Cyanide (P) inhibits cytochrome oxidase (Complex IV, entry 4), blocking electron transfer to oxygen and halting the ETC.
Antimycin A (Q) prevents electron transfer from cytochrome b to cytochrome c1 in Complex III (entry 2).
Valinomycin (R) acts as a K+ ionophore (entry 1), dissipating the proton gradient without affecting ETC directly.
Aurovertin (S) binds the F1 subunit of ATP synthase (entry 3), inhibiting ATP synthesis.
Option Analysis
Option (A) P-5, Q-2, R-3, S-1: Incorrect—Cyanide does not target adenine nucleotide translocase (5); Valinomycin is not F1 inhibitor (3); Aurovertin is not K+ ionophore (1).
Option (B) P-5, Q-2, R-1, S-3: Incorrect—Cyanide mismatches with 5 (translocase); correct for others but fails on P.
Option (C) P-4, Q-2, R-1, S-3: Correct—all matches align with known mechanisms.
Option (D) P-4, Q-5, R-3, S-1: Incorrect—Antimycin A is not translocase inhibitor (5); Valinomycin/Aurovertin swapped wrongly.
ETC inhibitors like Cyanide, Antimycin A, Valinomycin, and Aurovertin are essential topics in electron transport chain matching questions for biology exams. This Group I Group II matching guide explains their precise targets in mitochondrial respiration, helping students ace cytochrome oxidase inhibitors and ATP synthase blockers.
Inhibitor Mechanisms
These compounds disrupt oxidative phosphorylation at specific sites:
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Cyanide: Binds heme a3 in Complex IV (cytochrome oxidase), preventing O2 reduction and ATP production.
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Antimycin A: Targets Complex III, blocking electrons from cytochrome b to cytochrome c1.
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Valinomycin: Mobile carrier making it a K+ ionophore, collapsing membrane potential.
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Aurovertin: Specifically inhibits F1 subunit of ATP synthase, stopping rotary catalysis.
Why Option C Wins
In match the compounds Group I with Group II, only (C) P-4 (Cyanide-cytochrome oxidase), Q-2 (Antimycin A-electron transfer b to c1), R-1 (Valinomycin-K+ ionophore), S-3 (Aurovertin-F1) fits textbook mechanisms, avoiding mismatches like adenine nucleotide translocase.
Exam Tips for ETC Matching
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Recall: Complex IV inhibitors (cyanide, CO) vs. Complex III (antimycin).
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Ionophores (valinomycin) uncouple without ETC block.
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Use mnemonics: “Aurovertin ATP F1” for synthase.
Perfect for CSIR NET, NEET PG, or biochemistry MCQs on mitochondrial inhibitors.
