Part 8 – Respiration in Plants – Advanced NEET-level MCQs (Across All Subtopics)
📘 Part 8 – Respiration in Plants – Advanced NEET-level MCQs (Across All Subtopics)
Q1. During glycolysis, which step involves substrate-level phosphorylation?
a) Glucose → Glucose-6-phosphate
b) 1,3-Bisphosphoglycerate → 3-Phosphoglycerate
c) Phosphoenolpyruvate → Pyruvate
d) Both (b) and (c)
Answer: d) Both (b) and (c)
- a) Incorrect: This is phosphorylation using ATP, not substrate-level.
- **b) Correct step of SLP (ATP generated).
- **c) Correct step of SLP (ATP generated).
- d) Correct: Both steps are substrate-level phosphorylation in glycolysis.
Q2. Oxidative decarboxylation of pyruvate produces:
a) 1 CO₂ + 1 ATP + 1 NADH
b) 1 CO₂ + 1 NADH + 1 Acetyl CoA
c) 2 CO₂ + 1 FADH₂
d) 1 CO₂ + 1 ATP + 1 Acetyl CoA
Answer: b) 1 CO₂ + 1 NADH + 1 Acetyl CoA
- a) Incorrect: No ATP formed in this step.
- b) Correct: Pyruvate → Acetyl CoA + CO₂ + NADH.
- c) Incorrect: 2 CO₂ not released here.
- d) Incorrect: ATP is not directly formed.
Q3. Which complex of the electron transport chain directly reduces O₂ to H₂O?
a) Complex I
b) Complex II
c) Complex III
d) Complex IV
Answer: d) Complex IV
- a) Incorrect: NADH dehydrogenase transfers e⁻ to ubiquinone.
- b) Incorrect: Succinate dehydrogenase transfers e⁻ but not to O₂.
- c) Incorrect: Transfers e⁻ from ubiquinol to cytochrome c.
- d) Correct: Cytochrome oxidase (Complex IV) reduces O₂ to H₂O.
Q4. In fermentation, the primary purpose is:
a) To produce ethanol
b) To produce lactic acid
c) To regenerate NAD⁺
d) To generate maximum ATP
Answer: c) To regenerate NAD⁺
- a) Incorrect: Ethanol is a by-product in some organisms.
- b) Incorrect: Lactic acid is a by-product in animals.
- c) Correct: NADH must be oxidized to NAD⁺ to sustain glycolysis.
- d) Incorrect: ATP yield is minimal (only 2).
Q5. The P/O ratio for FADH₂ is:
a) 1
b) 2
c) 1.5
d) 3
Answer: b) 2
- a) Incorrect: Too low.
- b) Correct (as per NCERT): FADH₂ yields 2 ATP.
- c) Incorrect: Modern value, not NCERT standard.
- d) Incorrect: NADH yields 3 ATP, not FADH₂.
Q6. Which is NOT produced in TCA cycle directly?
a) NADH
b) ATP (or GTP)
c) FADH₂
d) Oxygen
Answer: d) Oxygen
- a) Incorrect: NADH is formed (3 per cycle).
- b) Incorrect: ATP (or GTP) formed at succinyl-CoA step.
- c) Incorrect: FADH₂ formed at succinate → fumarate step.
- d) Correct: Oxygen is not produced in TCA cycle.
Q7. Which intermediate connects glycolysis and TCA cycle?
a) Oxaloacetate
b) Acetyl CoA
c) Citrate
d) Fumarate
Answer: b) Acetyl CoA
- a) Incorrect: OAA is in TCA, not direct link.
- b) Correct: Pyruvate → Acetyl CoA enters TCA.
- c) Incorrect: Citrate is formed only after Acetyl CoA enters.
- d) Incorrect: Fumarate is a later TCA product.
Q8. Respiratory quotient of fat is less than 1 because:
a) More CO₂ is produced
b) Less O₂ is consumed
c) More O₂ is consumed, less CO₂ produced
d) No CO₂ is produced
Answer: c) More O₂ is consumed, less CO₂ produced
- a) Incorrect: Opposite is true.
- b) Incorrect: Fats require more O₂.
- c) Correct: β-oxidation of fats consumes more O₂.
- d) Incorrect: CO₂ is still produced.
Q9. Which step in glycolysis produces NADH?
a) Glucose → Glucose-6-phosphate
b) Fructose-6-phosphate → Fructose-1,6-bisphosphate
c) Glyceraldehyde-3-phosphate → 1,3-bisphosphoglycerate
d) Phosphoenolpyruvate → Pyruvate
Answer: c) Glyceraldehyde-3-phosphate → 1,3-bisphosphoglycerate
- a) Incorrect: Consumes ATP.
- b) Incorrect: Consumes ATP.
- c) Correct: NAD⁺ reduced to NADH here.
- d) Incorrect: Produces ATP, not NADH.
Q10. One turn of the TCA cycle yields:
a) 1 NADH, 1 FADH₂, 1 ATP
b) 2 NADH, 1 FADH₂, 1 ATP
c) 3 NADH, 1 FADH₂, 1 ATP
d) 3 NADH, 2 FADH₂, 2 ATP
Answer: c) 3 NADH, 1 FADH₂, 1 ATP
- a) Incorrect: Too low.
- b) Incorrect: Misses one NADH.
- c) Correct: Per acetyl-CoA → 3 NADH, 1 FADH₂, 1 ATP (or GTP).
- d) Incorrect: Overestimates.
Q11. Which molecule enters both respiration and photosynthesis as a key intermediate?
a) Pyruvate
b) Acetyl CoA
c) Glyceraldehyde-3-phosphate (G3P)
d) Oxaloacetate
Answer: c) Glyceraldehyde-3-phosphate (G3P)
- a) Incorrect: Pyruvate is respiratory only.
- b) Incorrect: Acetyl CoA not in photosynthesis.
- c) Correct: G3P is common to glycolysis and Calvin cycle.
- d) Incorrect: OAA is TCA, not photosynthesis.
Q12. Efficiency of anaerobic respiration compared to aerobic respiration is:
a) 2%
b) 7%
c) 30%
d) 50%
Answer: b) 7%
- a) Incorrect: Too low.
- b) Correct: Anaerobic respiration yields ~7% efficiency compared to aerobic.
- c) Incorrect: 30% is too high.
- d) Incorrect: 50% is aerobic efficiency.
Q13. The key regulatory enzyme of glycolysis is:
a) Hexokinase
b) Phosphofructokinase (PFK)
c) Pyruvate kinase
d) Enolase
Answer: b) Phosphofructokinase (PFK)
- a) Incorrect: Important but not the main regulatory point.
- b) Correct: Rate-limiting enzyme of glycolysis.
- c) Incorrect: Regulated but not the key step.
- d) Incorrect: Just a catalyzing enzyme.
Q14. Which statement about ETS is correct?
a) Electron flow releases energy in one step
b) ATP synthase functions as proton pump
c) Protons move from matrix to intermembrane space
d) Cytochrome c reduces NAD⁺
Answer: c) Protons move from matrix to intermembrane space
- a) Incorrect: Energy is released stepwise.
- b) Incorrect: ATP synthase allows protons back, not pump.
- c) Correct: Proton gradient formed across inner membrane.
- d) Incorrect: Cytochrome c carries electrons, not reduce NAD⁺.
Q15. Which substrate has highest RQ value?
a) Carbohydrate
b) Fat
c) Protein
d) Organic acid
Answer: d) Organic acid
- a) Incorrect: RQ = 1.
- b) Incorrect: RQ = 0.7.
- c) Incorrect: ~0.8.
- d) Correct: RQ >1.
Q16. The immediate electron acceptor of NADH in ETS is:
a) Cytochrome b
b) FMN (Flavin mononucleotide)
c) Ubiquinone
d) Oxygen
Answer: b) FMN (Flavin mononucleotide)
- a) Incorrect: Cytochrome b is downstream.
- b) Correct: FMN accepts electrons from NADH dehydrogenase.
- c) Incorrect: Ubiquinone receives later.
- d) Incorrect: O₂ is final acceptor, not immediate.
Q17. During anaerobic respiration in muscles, pyruvate is converted into:
a) Ethanol
b) Lactic acid
c) Acetyl CoA
d) Oxaloacetate
Answer: b) Lactic acid
- a) Incorrect: Occurs in yeast.
- b) Correct: In muscles, pyruvate → lactate.
- c) Incorrect: Requires O₂.
- d) Incorrect: Not part of anaerobic respiration.
Q18. ATP generated directly in TCA cycle is by:
a) Oxidative phosphorylation
b) Substrate-level phosphorylation
c) Photophosphorylation
d) Chemiosmosis
Answer: b) Substrate-level phosphorylation
- a) Incorrect: Happens via ETS, not TCA.
- b) Correct: Succinyl-CoA → Succinate forms ATP/GTP.
- c) Incorrect: Light-driven.
- d) Incorrect: Occurs in ETS.
Q19. Which of the following steps releases CO₂ in TCA cycle?
a) Isocitrate → α-ketoglutarate
b) α-ketoglutarate → Succinyl-CoA
c) Malate → Oxaloacetate
d) Both (a) and (b)
Answer: d) Both (a) and (b)
- a) Correct: Oxidative decarboxylation.
- b) Correct: Another decarboxylation step.
- c) Incorrect: Produces NADH, no CO₂.
- **d) Correct overall.
Q20. Net ATP from glycolysis + link reaction + TCA + ETS per glucose is:
a) 36
b) 38
c) 32
d) 40
Answer: b) 38
- a) Incorrect: Slight underestimate.
- b) Correct: NCERT assumes 38 ATP.
- c) Incorrect: Modern value for humans.
- d) Incorrect: Too high.
Q21. Which enzyme is NOT involved in oxidative decarboxylation of pyruvate?
a) Pyruvate dehydrogenase
b) Decarboxylase
c) Coenzyme A
d) ATP synthase
Answer: d) ATP synthase
- a) Incorrect: Present in complex.
- b) Incorrect: Helps release CO₂.
- c) Incorrect: Essential cofactor.
- d) Correct: ATP synthase is in ETS, not pyruvate decarboxylation.
Q22. The most direct evidence that TCA cycle is amphibolic:
a) Presence of ATP production
b) Formation of α-ketoglutarate used in amino acid synthesis
c) Release of CO₂
d) Use of O₂
Answer: b) Formation of α-ketoglutarate used in amino acid synthesis
- a) Incorrect: ATP is catabolic.
- b) Correct: Provides building blocks for biosynthesis.
- c) Incorrect: Just catabolic.
- d) Incorrect: Oxygen use is catabolic.
Q23. Which ETC complex does NOT pump protons?
a) Complex I
b) Complex II
c) Complex III
d) Complex IV
Answer: b) Complex II
- a) Incorrect: Pumps protons.
- b) Correct: Succinate dehydrogenase does not pump protons.
- c) Incorrect: Pumps protons.
- d) Incorrect: Pumps protons.
Q24. Which metabolite is common to both TCA cycle and gluconeogenesis?
a) Oxaloacetate
b) Citrate
c) Succinyl-CoA
d) Fumarate
Answer: a) Oxaloacetate
- a) Correct: OAA → PEP → glucose synthesis.
- b) Incorrect: Citrate links to fatty acid synthesis.
- c) Incorrect: Not directly gluconeogenic.
- d) Incorrect: Not a gluconeogenic precursor.
Q25. The ATP yield per NADH oxidized in ETS is:
a) 1
b) 2
c) 3
d) 4
Answer: c) 3
- a) Incorrect: Too low.
- b) Incorrect: This is for FADH₂.
- c) Correct (NCERT standard): 3 ATP per NADH.
- d) Incorrect: Too high.
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