Questions about Electron Transport (Electron Transport Chain - ETC)
20 multiple-choice questions about Electron Transport (Electron Transport Chain - ETC) with five alternatives each. The answers are presented at the end.
Multiple Choice Questions: Electron Transport
1. Where does the electron transport chain occur in eukaryotic cells?
A) Cytoplasm
B) Inner mitochondrial membrane
C) Outer mitochondrial membrane
D) Mitochondrial matrix
E) Golgi apparatus
2. What is the final electron acceptor in the electron transport chain?
A) NAD+
B) FAD
C) CO₂
D) Water
E) Oxygen
3. Which molecule donates electrons to Complex I of the ETC?
A) FADH₂
B) NADH
C) ATP
D) ADP
E) CO₂
4. Which molecule donates electrons to Complex II of the ETC?
A) NADH
B) Glucose
C) Pyruvate
D) FADH₂
E) Oxygen
5. What is formed when oxygen accepts electrons at the end of the ETC?
A) Ozone
B) Water
C) ATP
D) CO₂
E) Hydrogen gas
6. How many ATP molecules are generally produced from one NADH in the ETC?
A) 1
B) 2
C) 2.5
D) 3.5
E) 4
7. How many ATP molecules are produced from one FADH₂ in the ETC?
A) 1
B) 1.5
C) 2
D) 2.5
E) 3
8. What drives the production of ATP in the ETC?
A) Light energy
B) Glucose breakdown
C) Proton gradient
D) Pyruvate decarboxylation
E) Enzyme activation
9. Which enzyme synthesizes ATP in the ETC?
A) ATP kinase
B) ADP synthase
C) Cytochrome oxidase
D) ATP synthase
E) FAD oxidase
10. What is the main purpose of the electron transport chain?
A) To split glucose
B) To convert pyruvate into acetyl-CoA
C) To produce CO₂
D) To create a proton gradient and generate ATP
E) To break down fatty acids
11. How is the proton gradient generated during ETC?
A) By pumping protons from the cytoplasm into the matrix
B) By the breakdown of glucose
C) By electron movement through protein complexes
D) By the Krebs cycle
E) By water splitting
12. Which protein complex in the ETC does NOT pump protons?
A) Complex I
B) Complex II
C) Complex III
D) Complex IV
E) ATP synthase
13. Which component transfers electrons between Complex I and Complex III?
A) Cytochrome c
B) Ubiquinone (Coenzyme Q)
C) NADH
D) FADH₂
E) Oxygen
14. Which component transfers electrons between Complex III and Complex IV?
A) Coenzyme A
B) FAD
C) Cytochrome c
D) NADH
E) Pyruvate
15. What happens to the protons pumped into the intermembrane space?
A) They form water
B) They are used in the Krebs cycle
C) They power ATP synthase as they flow back
D) They form glucose
E) They are expelled from the cell
16. Which term describes the use of a proton gradient to drive ATP synthesis?
A) Substrate-level phosphorylation
B) Oxidative phosphorylation
C) Hydrolysis
D) Chemosynthesis
E) Fermentation
17. How many total ATP can be generated from one molecule of glucose through cellular respiration (including ETC)?
A) 18
B) 24
C) 30–32
D) 40–42
E) 50
18. What is the role of cytochrome c in the ETC?
A) Pumps protons
B) Accepts oxygen
C) Transfers electrons between complexes
D) Breaks down glucose
E) Synthesizes ATP
19. Which statement is TRUE about electron transport in prokaryotes?
A) It occurs in the nucleus
B) It does not require oxygen
C) It occurs in the plasma membrane
D) It uses light energy
E) It produces glucose
20. Which molecule is reduced at the end of the ETC?
A) NADH
B) FADH₂
C) ADP
D) Oxygen
E) Glucose
Answer Key
1. B – Inner mitochondrial membrane
2. E – Oxygen
3. B – NADH
4. D – FADH₂
5. B – Water
6. C – 2.5
7. B – 1.5
8. C – Proton gradient
9. D – ATP synthase
10. D – To create a proton gradient and generate ATP
11. C – By electron movement through protein complexes
12. B – Complex II
13. B – Ubiquinone (Coenzyme Q)
14. C – Cytochrome c
15. C – They power ATP synthase as they flow back
16. B – Oxidative phosphorylation
17. C – 30–32
18. C – Transfers electrons between complexes
19. C – It occurs in the plasma membrane
20. D – Oxygen
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