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9.4 Electron Transport Chain — Test 1
Q1. The first electron acceptor of the NADH dehydrogenase complex (Complex I) is:✓ FMN
Q2. Which ETC complex moves electrons from a lipid-soluble carrier to a water-soluble mobile carrier?✓ Complex III
Q3. Which of the following is an electron donor in the ETC?✓ FADH₂
Q4. Which of the following is an electron donor? (variant)✓ FADH₂
Q5. Match each ETC feature to the correct complex:✓ 1-Complex II, 2-Complex III, 3-Complex IV
Q6. Which compound is the electron donor in most reductive biosynthesis?✓ NADPH
Q7. Which one of the following is an uncoupler of electron transport and oxidative phosphorylation?✓ 2,4-dinitrophenol
Q8. The alternative oxidase (AOX) pathway has which features? (i) transfers electrons from ubiquinol to O₂; (ii) five ATP synthesised; (iii) multi-enzyme complex; (iv) ~32 kDa.✓ (i) and (iv)
Q9. Identify correct statements about alternative oxidase (AOX): i) found in plants, algae, fungi, protozoa; ii) transfers electrons from ubiquinol to O₂ bypassing cytochrome c oxidase; iii) transfers electrons from ubiquinone to O₂; iv) encoded by mitochondrial genome.✓ i and ii
Q10. Which compound blocks electron transfer from cytochrome b to cytochrome c1 (within Complex III)?✓ Antimycin A
Q11. Which ETC inhibitor is a secondary metabolite of Streptomyces sp.?✓ Antimycin A
Q12. F1 particles (elementary particles) of mitochondria are found:✓ Projecting from the cristae (matrix side of inner membrane)
Q13. Atractyloside interferes with oxidative phosphorylation by:✓ Inhibiting the adenine nucleotide translocase
Q14. Cyanide is a non-competitive inhibitor of which enzyme?✓ Cytochrome c oxidase
Q15. Cyanide blocks the electron transport chain at:✓ Cytochrome a+a3 (Complex IV)
Q16. Cyanide blocks the electron transport chain at (variant):✓ Cytochrome a+a3
Q17. The copper-containing mitochondrial enzyme is:✓ Cytochrome c oxidase
Q18. Cyanide inhibits:✓ Cytochrome c oxidase
Q19. In cytochrome c oxidase, protons pass through two channels (K and D pathways). How many protons pass through the K and D pathways respectively per catalytic cycle?✓ 2 and 4
Q20. Cytochromes function in:✓ Electron transport
Q21. Cytochromes are found in the:✓ Inner mitochondrial membrane
Q22. Dinitrophenol, an uncoupler of oxidative phosphorylation:✓ Allows electron transport to continue without ATP synthesis
Q23. The electron carrier that can act at the junction between a two-electron donor and a one-electron acceptor is:✓ Ubiquinone (CoQ)
9.4 Electron Transport Chain — Test 2
Q24. Electrons do not usually flow through the ETC to O₂ unless:✓ ADP is simultaneously phosphorylated to ATP
Q25. Which of the following is NOT an inhibitor of the electron transport chain?✓ Dinitrophenol
Q26. Which of the following is NOT an inhibitor of the ETC? (variant)✓ Dinitrophenol
Q27. The electron transport chain is located in the:✓ Inner mitochondrial membrane
Q28. The correct sequence of electron carriers in the ETC is:✓ NADH dehydrogenase → ubiquinone → cytochrome a+a3
Q29. In the ETC, FMN can adopt which highest oxidation state, and accepts/donates how many electrons?✓ Oxidation state 2; 1 or 2 electrons
Q30. The proton pumps of the inner mitochondrial membrane (ETC complexes) and ATP synthase are of which ATPase type for ATP synthesis?✓ F-type
Q31. Which compartment becomes acidic (high H⁺) during mitochondrial electron transport?✓ Intermembrane space
Q32. The prosthetic group of NADH dehydrogenase (Complex I) is:✓ FMN
Q33. Oligomycin inhibits which process?✓ ATP synthase (F0 proton channel)
Q34. Which ATPase pump is the target of oligomycin?✓ F0F1 ATP synthase
Q35. Which complex pumps the most protons across the inner membrane?✓ Complex I (NADH dehydrogenase)
Q36. Which ETC complex does NOT pump protons out of the matrix?✓ Complex II
Q37. Which one of the following is NOT a proton pump?✓ Succinate-Q reductase (Complex II)
Q38. Mitochondrial supercomplexes (respirasomes) are usually formed mainly with:✓ Complexes III & IV (with I)
Q39. The Rieske iron-sulfur protein is located in which complex?✓ Complex III
Q40. Which redox centre in the respiratory chain does NOT possess a prosthetic group?✓ Ubiquinone
Q41. Which is TRUE about ubiquinone (coenzyme Q)?✓ It is small, hydrophobic and shuttles electrons between complexes
Q42. An uncoupler of oxidative phosphorylation would most likely lead to:✓ Operation of the ETC without ATP production
Q43. An uncoupler of oxidative phosphorylation would most likely lead to (variant):✓ Electron transport without ATP production
Q44. Which compound increases the rate of mitochondrial respiration (O₂ consumption)?✓ Dinitrophenol
Q45. Which of the following increases the rate of respiration of mitochondria? (variant)✓ Dinitrophenol / uncoupler proteins