CHEM 210 Module 8 Exam | Biochemistry | Portage Learning | Q & A | 2026 Edition

CHEM 210 Module 8 Exam | Biochemistry | Portage Learning | Q & A | 2026
Edition


SECTION 1: ELECTRON TRANSPORT CHAIN (ETC) – COMPLEXES & ELECTRON
FLOW (Questions 1–40)


1. How many complexes are associated with the electron transport chain
(ETC)? - A) Three - B) Four - C) Five - D) Six
Answer C: ) Five
Rationale: The ETC has five complexes: Complex I (NADH dehydrogenase),
Complex II (succinate dehydrogenase), Complex III (cytochrome bc₁), Complex
IV (cytochrome c oxidase), and Complex V (ATP synthase).




2. True or False: There are six complexes associated with the ETC. - A) False -
B) True
Answer A: ) False

,Rationale: The ETC has five complexes, not six. Complexes I–IV transport
electrons, and Complex V (ATP synthase) produces ATP.




3. Which complex of the ETC accepts electrons from NADH? - A) Complex I -
B) Complex II - C) Complex III - D) Complex IV
Answer A: ) Complex I
Rationale: Complex I (NADH dehydrogenase) accepts electrons from NADH
and transfers them to ubiquinone (coenzyme Q).




4. Which complex of the ETC accepts electrons from FADH₂? - A) Complex I -
B) Complex II - C) Complex III - D) Complex IV
Answer B: ) Complex II
Rationale: Complex II (succinate dehydrogenase) accepts electrons from
FADH₂ and transfers them to ubiquinone. FADH₂ enters the ETC at Complex II,
bypassing Complex I.




5. FADH₂ donates electrons and H⁺ to complex ______. - A) I - B) II - C) III - D)
IV
Answer B: ) II

,Rationale: FADH₂ enters the ETC at Complex II (succinate dehydrogenase),
which is also part of the citric acid cycle.




6. Which complex of the ETC transfers electrons from ubiquinol to
cytochrome c? - A) Complex I - B) Complex II - C) Complex III - D) Complex IV
Answer C: ) Complex III
Rationale: Complex III (cytochrome bc₁) transfers electrons from ubiquinol
(QH₂) to cytochrome c.




7. Which complex of the ETC transfers electrons from cytochrome c to
molecular oxygen (O₂)? - A) Complex I - B) Complex II - C) Complex III - D)
Complex IV
Answer D: ) Complex IV
Rationale: Complex IV (cytochrome c oxidase) transfers electrons from
cytochrome c to molecular oxygen, reducing O₂ to H₂O.




8. What is the final electron acceptor in the electron transport chain? - A)
NAD⁺ - B) FAD - C) Oxygen (O₂) - D) Cytochrome c
Answer C: ) Oxygen (O₂)

, Rationale: Molecular oxygen is the final electron acceptor in the ETC,
combining with electrons and protons to form water.




9. What is the role of ubiquinone (coenzyme Q) in the ETC? - A) It accepts
electrons from cytochrome c - B) It serves as a mobile electron carrier
between Complexes I/II and III - C) It pumps protons across the membrane -
D) It reduces oxygen to water
Answer B: ) It serves as a mobile electron carrier between Complexes I/II and
III
Rationale: Ubiquinone (coenzyme Q) is a lipid-soluble mobile electron carrier
that shuttles electrons from Complexes I and II to Complex III.




10. What is the role of cytochrome c in the ETC? - A) It accepts electrons
from NADH - B) It transfers electrons from Complex III to Complex IV - C) It
serves as a mobile electron carrier between Complexes III and IV - D) It
reduces oxygen to water
Answer C: ) It serves as a mobile electron carrier between Complexes III and
IV
Rationale: Cytochrome c is a water-soluble mobile electron carrier that
transfers electrons from Complex III to Complex IV.