Part 7 — Respiratory Balance Sheet, Amphibolic Pathway & Respiratory Quotient (25 MCQs)
📘 Part 7 – Respiratory Balance Sheet, Amphibolic Pathway & Respiratory Quotient (RQ) – Critical / NEET-level
Q1. The maximum ATP yield from complete oxidation of one glucose molecule in eukaryotes is:
a) 30
b) 32
c) 36
d) 38
Answer: d) 38
- a) 30 – Incorrect: This is a modern estimate for mammalian mitochondria due to proton leakage.
- b) 32 – Incorrect: Represents a revised calculation in humans using P/O ratios (not NCERT standard).
- c) 36 – Incorrect: Earlier estimate but considered slightly lower than NCERT’s classic calculation.
- d) 38 – Correct: As per NCERT, 38 ATP are produced in eukaryotes from one glucose molecule.
Q2. The term “net ATP gain” in glycolysis refers to:
a) ATP formed – ATP consumed
b) Only substrate-level phosphorylation
c) Only oxidative phosphorylation
d) Total ATP in aerobic respiration
Answer: a) ATP formed – ATP consumed
- a) Correct: Glycolysis forms 4 ATP, consumes 2 → net = 2 ATP.
- b) Incorrect: Only counts ATP made, ignores consumption.
- c) Incorrect: Glycolysis does not involve oxidative phosphorylation.
- d) Incorrect: Refers to overall respiration, not glycolysis.
Q3. Which of the following is NOT considered while preparing the respiratory balance sheet?
a) ATP consumed in transporting NADH to mitochondria
b) Substrate-level phosphorylation
c) Efficiency of ATP yield
d) Oxygen availability
Answer: a) ATP consumed in transporting NADH to mitochondria
- a) Correct: NCERT assumes NADH enters mitochondria freely (ignores transport cost).
- b) Incorrect: It is counted, e.g., 2 ATP in glycolysis, 1 in TCA.
- c) Incorrect: Efficiency (~50–70%) is considered.
- d) Incorrect: Oxygen presence is necessary in aerobic respiration.
Q4. The efficiency of aerobic respiration in plants is around:
a) 100%
b) 70%
c) 50%
d) 30%
Answer: c) 50%
- a) Incorrect: Impossible—energy is lost as heat.
- b) Incorrect: 70% is too high.
- c) Correct: NCERT says ~50% efficiency.
- d) Incorrect: 30% is lower than actual.
Q5. If 1 molecule of palmitic acid (16C) is oxidized, the number of ATP molecules produced is approximately:
a) 38
b) 129
c) 146
d) 64
Answer: b) 129
- a) Incorrect: This is for glucose, not fatty acid.
- b) Correct: Palmitic acid oxidation yields ~129 ATP.
- c) Incorrect: 146 ATP is for longer fatty acids.
- d) Incorrect: 64 ATP is too low.
Q6. Which pathway is considered amphibolic?
a) Glycolysis
b) Krebs cycle
c) Fermentation
d) Calvin cycle
Answer: b) Krebs cycle
- a) Incorrect: Mainly catabolic.
- b) Correct: Acts both catabolically (energy release) and anabolically (precursors for amino acids, nucleotides).
- c) Incorrect: Only catabolic.
- d) Incorrect: Exclusively anabolic.
Q7. Respiratory Quotient (RQ) for glucose is:
a) 0.7
b) 1.0
c) >1.0
d) 0.9
Answer: b) 1.0
- a) Incorrect: 0.7 is for fats.
- b) Correct: Glucose breakdown → 6 CO₂ / 6 O₂ = 1.
- c) Incorrect: >1 occurs during organic acid respiration.
- d) Incorrect: 0.9 is not typical.
Q8. An RQ less than 1 indicates predominant respiration of:
a) Carbohydrates
b) Fats
c) Proteins
d) Organic acids
Answer: b) Fats
- a) Incorrect: Carbohydrate RQ = 1.
- b) Correct: Fats yield more O₂ consumption than CO₂, so RQ <1.
- c) Incorrect: Proteins usually ~0.8, not general.
- d) Incorrect: Organic acids give RQ >1.
Q9. RQ value for anaerobic respiration in glucose is:
a) 0.7
b) 1.0
c) Infinity
d) Zero
Answer: c) Infinity
- a) Incorrect: Not fats.
- b) Incorrect: Aerobic respiration of glucose = 1.
- c) Correct: CO₂ released, O₂ not used → denominator = 0 → RQ = ∞.
- d) Incorrect: Zero would mean CO₂ not produced.
Q10. Which statement about the respiratory balance sheet is FALSE?
a) Assumes complete oxidation of one glucose
b) Assumes NADH freely enters mitochondria
c) Assumes no intermediates are withdrawn
d) Accounts for loss of energy as heat
Answer: d) Accounts for loss of energy as heat
- a) Correct: Complete oxidation assumed.
- b) Correct: Transport cost ignored.
- c) Correct: No diversion of intermediates assumed.
- d) Correct Answer: It does not account for heat loss.
Q11. If an organic acid is the respiratory substrate, the RQ value would be:
a) <1
b) =1
c) >1
d) =0
Answer: c) >1
- a) Incorrect: Indicates fat.
- b) Incorrect: Indicates carbohydrate.
- c) Correct: Organic acids release more CO₂ than O₂ consumed.
- d) Incorrect: Zero RQ means no CO₂ released.
Q12. Amphibolic nature of TCA cycle means:
a) It produces only ATP
b) It functions only in catabolism
c) It functions in both breakdown and synthesis
d) It functions only in photosynthesis
Answer: c) It functions in both breakdown and synthesis
- a) Incorrect: Also provides precursors.
- b) Incorrect: Not purely catabolic.
- c) Correct: Catabolic (oxidizing pyruvate) + anabolic (precursors).
- d) Incorrect: Not related to photosynthesis.
Q13. Which step of the TCA cycle directly shows amphibolic role?
a) Conversion of citrate to isocitrate
b) α-ketoglutarate acting as precursor for amino acids
c) Oxidation of succinate
d) Oxidation of fumarate
Answer: b) α-ketoglutarate acting as precursor for amino acids
- a) Incorrect: Just rearrangement.
- b) Correct: α-ketoglutarate → glutamate, transamination reactions.
- c) Incorrect: Oxidative step, not anabolic.
- d) Incorrect: Same as above.
Q14. RQ of proteins is generally:
a) 0.7
b) 1.0
c) ~0.8
d) ∞
Answer: c) ~0.8
- a) Incorrect: Fat value.
- b) Incorrect: Carbohydrate value.
- c) Correct: Proteins give less CO₂ per O₂ → ~0.8.
- d) Incorrect: Infinity is anaerobic respiration.
Q15. Which is NOT a limitation of the respiratory balance sheet?
a) It ignores transport of reducing equivalents
b) It assumes no side reactions
c) It ignores use of ATP for maintenance
d) It calculates energy loss as heat
Answer: d) It calculates energy loss as heat
- a) Correct: NADH transport not considered.
- b) Correct: Assumes no diversion.
- c) Correct: Maintenance costs ignored.
- d) Correct Answer: It does NOT calculate heat loss.
Q16. The complete oxidation of 1 molecule of glucose through respiration releases energy equivalent to:
a) 2870 kJ
b) 129 kJ
c) 38 kJ
d) 287 kJ
Answer: a) 2870 kJ
- a) Correct: Glucose oxidation releases ~2870 kJ/mol.
- b) Incorrect: Too low.
- c) Incorrect: 38 ATP is number of molecules, not energy in kJ.
- d) Incorrect: Ten times smaller.
Q17. RQ value greater than 1 is observed in:
a) Protein respiration
b) Fat respiration
c) Organic acid respiration
d) Anaerobic respiration
Answer: c) Organic acid respiration
- a) Incorrect: ~0.8, <1.
- b) Incorrect: 0.7, <1.
- c) Correct: CO₂ > O₂ → RQ >1.
- d) Incorrect: Anaerobic respiration → RQ = ∞.
Q18. In amphibolic pathway, fatty acids enter respiration as:
a) Glucose
b) Acetyl CoA
c) Citrate
d) Oxaloacetate
Answer: b) Acetyl CoA
- a) Incorrect: Fatty acids never form glucose directly.
- b) Correct: Fatty acids undergo β-oxidation → Acetyl CoA.
- c) Incorrect: Acetyl CoA enters TCA to form citrate.
- d) Incorrect: OAA is from pyruvate/amino acids.
Q19. RQ can never be:
a) 0
b) 0.7
c) 1.0
d) ∞
Answer: a) 0
- a) Correct: RQ = 0 means CO₂ not released → respiration impossible.
- b) Incorrect: 0.7 is valid (fats).
- c) Incorrect: 1.0 is valid (carbs).
- d) Incorrect: ∞ is valid (anaerobic).
Q20. In plants, the assumption that NADH from glycolysis directly enters mitochondria is:
a) True, universally
b) True for prokaryotes
c) False, but assumed in balance sheet
d) True, but only in anaerobic respiration
Answer: c) False, but assumed in balance sheet
- a) Incorrect: Not true universally.
- b) Incorrect: In prokaryotes mitochondria are absent.
- c) Correct: Assumed in balance sheet to simplify ATP calculation.
- d) Incorrect: Anaerobic respiration doesn’t involve mitochondria.
Q21. Which intermediate links carbohydrate and fat metabolism in amphibolic pathway?
a) Pyruvate
b) Acetyl CoA
c) Citrate
d) α-ketoglutarate
Answer: b) Acetyl CoA
- a) Incorrect: Before fatty acid oxidation.
- b) Correct: Common intermediate for carbohydrate, protein, and fat catabolism.
- c) Incorrect: Downstream intermediate.
- d) Incorrect: Amino acid precursor, not fat link.
Q22. Which intermediate links protein metabolism to TCA cycle?
a) Fumarate
b) α-ketoglutarate
c) Citrate
d) Malate
Answer: b) α-ketoglutarate
- a) Incorrect: Minor link.
- b) Correct: Formed from glutamate, key link.
- c) Incorrect: Used in fatty acid synthesis.
- d) Incorrect: Malate is less direct.
Q23. Respiratory Quotient is defined as:
a) O₂ consumed / CO₂ released
b) CO₂ released / O₂ consumed
c) ATP produced / O₂ consumed
d) CO₂ released / ATP produced
Answer: b) CO₂ released / O₂ consumed
- a) Incorrect: Inverse of correct.
- b) Correct: Standard definition.
- c) Incorrect: That’s P/O ratio.
- d) Incorrect: Not a standard definition.
Q24. Which statement is TRUE for RQ value?
a) RQ = 1 for fats
b) RQ = 0.7 for proteins
c) RQ > 1 for organic acids
d) RQ = ∞ for proteins
Answer: c) RQ > 1 for organic acids
- a) Incorrect: Fats → 0.7.
- b) Incorrect: Proteins → ~0.8.
- c) Correct: Organic acids release more CO₂.
- d) Incorrect: ∞ is for anaerobic respiration.
Q25. Which condition leads to RQ = ∞ ?
a) Carbohydrate oxidation
b) Fat oxidation
c) Anaerobic respiration of glucose
d) Protein oxidation
Answer: c) Anaerobic respiration of glucose
- a) Incorrect: RQ = 1.
- b) Incorrect: RQ = 0.7.
- c) Correct: O₂ not used, CO₂ released → RQ = ∞.
- d) Incorrect: ~0.8, not ∞.
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