Respiratory Balance Sheet & RQ — NEET Biology MCQs with Solutions
Free NEET Biology Respiratory Balance Sheet & RQ MCQs with step-by-step solutions (49 questions). Part of Respiration in Plants. Practise online on Prepizo — no login needed.
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Questions with solutions
Q1 — Respiratory Balance Sheet & RQ · easy · theory
The ratio of the volume of CO₂ evolved to O₂ consumed in respiration is called the:
A. Compensation point
B. Metabolic rate
C. Photosynthetic quotient
D. Respiratory Quotient (RQ) ✓ Correct
Solution: RQ = volume of CO₂ released / volume of O₂ used, and depends on the respiratory substrate.
Q2 — Respiratory Balance Sheet & RQ · easy · theory
When carbohydrates are the respiratory substrate, the RQ is:
A. 0.7
B. 1.0 ✓ Correct
C. Infinity
D. 0.9
Solution: For carbohydrates (e.g. glucose), CO₂ produced = O₂ consumed, so RQ = 1.
Q3 — Respiratory Balance Sheet & RQ · medium · theory
For fats as the respiratory substrate, the RQ is:
A. Less than 1 (about 0.7) ✓ Correct
B. Equal to 1
C. Exactly 0
D. Greater than 1
Solution: Fats need more O₂ (they are less oxidised), giving RQ ≈ 0.7.
Q4 — Respiratory Balance Sheet & RQ · medium · theory
The amphibolic nature of the respiratory pathway means it:
A. Does not involve intermediates
B. Only builds molecules
C. Is only catabolic
D. Serves in both breakdown (catabolism) and synthesis (anabolism) ✓ Correct
Solution: Respiratory intermediates (e.g. acetyl CoA, OAA) are drawn off to synthesise fats, amino acids, etc. — hence amphibolic.
Q5 — Respiratory Balance Sheet & RQ · hard · theory
An RQ greater than 1 (or approaching infinity) is characteristic of ______ respiration:
A. Protein
B. Fat
C. Anaerobic (fermentation, where CO₂ is released without O₂ uptake) ✓ Correct
D. Aerobic carbohydrate
Solution: In anaerobic respiration CO₂ is released while O₂ is not consumed, so RQ > 1 (or infinite).
Q6 — Respiratory Balance Sheet & RQ · hard · theory
The assumptions in the standard respiratory balance sheet (38 ATP) include all EXCEPT:
A. ATP is used only when required
B. Glycolysis, TCA and ETS pathways operate at different times in a stepwise sequential manner ✓ Correct
C. NADH is oxidised via the ETS
D. A sequential, orderly pathway with one substrate
Solution: In reality the pathways occur simultaneously and are not neatly sequential, so the 38-ATP figure is a theoretical maximum.
Q7 — Respiratory Balance Sheet & RQ · easy · numerical
The theoretical net gain of 38 ATP per glucose in the standard respiratory balance sheet is arrived at by adding which three contributions?
A. 8 (glycolysis) + 6 (Krebs) + 24 (oxidative phosphorylation)
B. 2 (glycolysis) + 6 (Krebs) + 30 (oxidative phosphorylation)
C. 2 (net glycolysis) + 2 (Krebs, substrate-level) + 34 (oxidative phosphorylation) ✓ Correct
D. 4 (glycolysis) + 4 (Krebs) + 30 (oxidative phosphorylation)
Solution: Net substrate-level ATP is 2 (glycolysis) + 2 (Krebs), and oxidative phosphorylation contributes 34, giving the conventional 38 ATP per glucose.
Q8 — Respiratory Balance Sheet & RQ · easy · numerical
The respiratory quotient (RQ) for the oxidation of a pure carbohydrate such as glucose is:
A. Greater than 1.0, because CO₂ released exceeds O₂ consumed
B. About 0.9, intermediate between fats and carbohydrates
C. Exactly 1.0, because the volumes of CO₂ released and O₂ consumed are equal ✓ Correct
D. About 0.7, because more O₂ is consumed than CO₂ released
Solution: For C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O, six CO₂ are produced for six O₂ used, so RQ = 6/6 = 1.0.
Q9 — Respiratory Balance Sheet & RQ · easy · numerical
When proteins are used as the respiratory substrate, the RQ is:
A. About 0.9 ✓ Correct
B. About 0.7
C. Greater than 1.0
D. Exactly 1.0
Solution: Protein respiration gives an RQ of roughly 0.9, reflecting that slightly less CO₂ is evolved than O₂ consumed.
Q10 — Respiratory Balance Sheet & RQ · medium · numerical
In living cells the assumptions of the standard 38-ATP balance sheet rarely hold. Which of the following is a reason the actual yield is lower (often taken as about 36 ATP)?
A. Oxygen is not actually required for the electron transport system
B. The Krebs cycle turns only once per glucose molecule
C. Intermediates are constantly withdrawn for other biosynthetic pathways and NADH may be shuttled at an energetic cost ✓ Correct
D. Glycolysis stops producing pyruvate under aerobic conditions
Solution: The 38-ATP figure assumes a sequential, unbroken pathway with all substrate going only to ATP. In reality intermediates are siphoned off for synthesis and cytoplasmic NADH import costs energy, lowering the real yield.
Q11 — Respiratory Balance Sheet & RQ · easy · numerical
A germinating castor bean seed, rich in stored oil, is respiring. What RQ would you expect, and why?
A. Less than 1 (around 0.7), because fatty acids are highly reduced and consume much O₂ relative to the CO₂ produced ✓ Correct
B. Exactly 0.5, because half the oxygen is stored
C. Exactly 1.0, because all seeds respire carbohydrates
D. Greater than 1.0, because fats release extra CO₂ without using O₂
Solution: Fats are highly reduced, so their oxidation needs a large amount of O₂ compared with the CO₂ released, giving an RQ well below 1 (about 0.7) — typical of fat-storing germinating seeds.
Q12 — Respiratory Balance Sheet & RQ · medium · numerical
A succulent plant respiring organic acids may show an RQ greater than 1, sometimes approaching infinity. Which situation gives an RQ that tends toward infinity?
A. Oxidation of fats, where O₂ greatly exceeds CO₂
B. Aerobic respiration of glucose, where CO₂ equals O₂
C. Protein oxidation, where CO₂ is slightly less than O₂
D. Anaerobic respiration/fermentation, where CO₂ is released but essentially no O₂ is consumed ✓ Correct
Solution: In fermentation, CO₂ is evolved (e.g. in alcoholic fermentation) while virtually no O₂ is taken up, so the RQ = CO₂/O₂ tends toward infinity.
Q13 — Respiratory Balance Sheet & RQ · medium · numerical
Match the substrate with its approximate RQ: (i) carbohydrate (ii) fat (iii) protein (iv) organic acid, with values (p) 1.0 (q) 0.7 (r) 0.9 (s) >1.0.
A. (i)-(p), (ii)-(q), (iii)-(r), (iv)-(s) ✓ Correct
B. (i)-(s), (ii)-(r), (iii)-(q), (iv)-(p)
C. (i)-(r), (ii)-(s), (iii)-(p), (iv)-(q)
D. (i)-(q), (ii)-(p), (iii)-(s), (iv)-(r)
Solution: Carbohydrate RQ = 1.0, fat ≈ 0.7, protein ≈ 0.9, and organic acids give RQ > 1.0 (more CO₂ than O₂).
Q14 — Respiratory Balance Sheet & RQ · medium · numerical
Assertion (A): In a living plant cell, a pure respiratory substrate is seldom respired in isolation. Reason (R): Usually a mixture of carbohydrates, fats and proteins is used, so the measured RQ is rarely exactly that of any single substrate.
A. Both A and R are true but R is not the correct explanation of A
B. A is false but R is true
C. Both A and R are true and R is the correct explanation of A ✓ Correct
D. A is true but R is false
Solution: Cells generally oxidise a mixture of substrates, so the observed RQ is an average and rarely equals the clean value of a single pure substrate.
Q15 — Respiratory Balance Sheet & RQ · medium · numerical
Considering the whole amphibolic respiratory pathway, why is it inaccurate to think of it as a pure catabolic (breakdown) pathway when constructing a strict ATP balance sheet?
A. The pathway synthesises glucose from CO₂ using ATP
B. Intermediates such as acetyl CoA and α-ketoglutarate are drawn off for synthesis, so not all substrate proceeds to ATP ✓ Correct
C. All intermediates are converted to oxygen
D. ATP is never actually produced during respiration
Solution: Because respiratory intermediates are continually withdrawn for anabolism (fatty acids from acetyl CoA, amino acids from α-ketoglutarate, etc.), the pathway is amphibolic, and a clean catabolic ATP tally is only theoretical.
Q16 — Respiratory Balance Sheet & RQ · medium · numerical
The 38-ATP balance sheet assumes an "orderly, sequential" operation of the pathway. Which of the following is NOT one of the stated assumptions behind this figure?
A. That no intermediates are withdrawn to synthesise other compounds
B. That NADH is fully oxidised by the electron transport system
C. That the substrate enters the pathway irregularly, with several substrates being metabolised at random times ✓ Correct
D. That glycolysis, the Krebs cycle and the ETS operate in a sequential, orderly pathway
Solution: The idealised balance sheet assumes an orderly sequential pathway, complete oxidation of NADH, and no withdrawal of intermediates. It does NOT assume irregular, random entry of multiple substrates — that would break the assumptions.
Q17 — Respiratory Balance Sheet & RQ · easy · theory
What is the net gain of ATP molecules during aerobic respiration of one glucose molecule?
A. 36 ATP
B. 38 ATP ✓ Correct
C. 34 ATP
D. 40 ATP
Solution: Complete aerobic respiration of one glucose yields a net of 38 ATP.
Q18 — Respiratory Balance Sheet & RQ · medium · theory
Match the following stages with their location: 1. Glycolysis, 2. TCA, 3. ETC with i. Mitochondrial matrix, ii. Cytoplasm, iii. Inner membrane of mitochondria.
A. 1-ii, 2-iii, 3-i
B. 1-i, 2-ii, 3-iii
C. 1-iii, 2-ii, 3-i
D. 1-ii, 2-i, 3-iii ✓ Correct
Solution: Glycolysis occurs in cytoplasm, TCA in the mitochondrial matrix, and ETC on the inner mitochondrial membrane.
Q19 — Respiratory Balance Sheet & RQ · medium · theory
The respiratory balance sheet is calculated on some assumptions. Which of the following assumptions is correct?
A. NADH is transferred to the chloroplast where oxidative phosphorylation occurs
B. Substrates are respired from many different molecules at once
C. The pathway is non-sequential for a given glucose molecule
D. Only glucose is the substrate and no other substrate or intermediate enters or leaves the pathway ✓ Correct
Solution: A key assumption is that glucose is the sole substrate with no intermediate entering or leaving the pathway.
Q20 — Respiratory Balance Sheet & RQ · easy · theory
In the balance sheet of fermentation, the net gain is
A. 8 ATP molecules
B. 38 ATP molecules
C. 2 ATP molecules ✓ Correct
D. 12 ATP molecules
Solution: Fermentation gives a net gain of only 2 ATP molecules per glucose.
Q21 — Respiratory Balance Sheet & RQ · medium · theory
Reoxidation of NADH to NAD+ is
A. Faster in aerobic respiration than in fermentation ✓ Correct
B. Faster in fermentation than in aerobic respiration
C. Equal in fermentation and aerobic respiration
D. Not possible in aerobic respiration
Solution: Aerobic respiration continuously reoxidises NADH through the ETS, so it is faster than the limited reoxidation in fermentation.
Q22 — Respiratory Balance Sheet & RQ · medium · theory
Which among the following is wrong? i. Other than glucose, no other substrate can be used in the respiratory process. ii. The respiratory pathway is an amphibolic pathway. iii. Different substrates enter at different stages in the respiratory pathway.
A. Both i and ii
B. Only ii
C. Only i ✓ Correct
D. Only iii
Solution: Fats, proteins and other substrates can also be respired, so statement i is wrong.
Q23 — Respiratory Balance Sheet & RQ · medium · theory
Fats, as a respiratory substrate, convert to which compounds first?
A. Pyruvic acid
B. Acetyl CoA
C. Glycerol and fatty acids ✓ Correct
D. Dihydroxyacetone phosphate
Solution: Fats are first broken down into glycerol and fatty acids before entering the respiratory pathway.
Q24 — Respiratory Balance Sheet & RQ · medium · theory
Match the substrate with the intermediate it enters as: 1. Amino acids, 2. Fatty acid, 3. Glycerol with i. Pyruvic acid, ii. Dihydroxyacetone phosphate, iii. Acetyl CoA.
A. 1-iii, 2-i, 3-ii
B. 1-ii, 2-i, 3-iii
C. 1-i, 2-iii, 3-ii ✓ Correct
D. 1-ii, 2-iii, 3-i
Solution: Amino acids enter as pyruvic acid, fatty acids as acetyl CoA, and glycerol as dihydroxyacetone phosphate.
Q25 — Respiratory Balance Sheet & RQ · easy · theory
What is the RQ if carbohydrates are used as respiratory substrate?
A. 0.9
B. 1 ✓ Correct
C. 0.7
D. 0.8
Solution: For carbohydrates, CO2 released equals O2 consumed, so RQ = 1.
Q26 — Respiratory Balance Sheet & RQ · medium · theory
What is the final end product yield of the TCA cycle (per acetyl CoA)?
A. Only 1 ATP
B. Only 3 NADH + H+
C. 3 NADH + H+, 1 FADH2 and 1 ATP/GTP ✓ Correct
D. Only 1 FADH2
Solution: Per acetyl CoA the TCA cycle yields 3 NADH + H+, 1 FADH2 and 1 ATP (GTP).
Q27 — Respiratory Balance Sheet & RQ · medium · theory
Which statement is true about RQ? i. It is also called the respiratory ratio. ii. It is the volume of O2 released over the volume of CO2 evolved. iii. RQ of different substrates is different.
A. All of the above
B. Only i
C. Only iii
D. Both i and iii ✓ Correct
Solution: RQ (respiratory ratio) is CO2 evolved over O2 consumed and differs by substrate, so ii is wrong while i and iii are correct.
Q28 — Respiratory Balance Sheet & RQ · easy · theory
Choose the correct definition of RQ.
A. RQ = volume of O2 evolved / volume of CO2 consumed
B. RQ = volume of CO2 consumed / volume of O2 evolved
C. RQ = volume of O2 consumed / volume of CO2 evolved
D. RQ = volume of CO2 evolved / volume of O2 consumed ✓ Correct
Solution: Respiratory quotient = CO2 released / O2 consumed.
Q29 — Respiratory Balance Sheet & RQ · medium · theory
What will be the RQ for the equation: 2(C51H98O6) + 145O2 -> 102CO2 + 98H2O + Energy?
A. 1
B. 0.9
C. 0.7 ✓ Correct
D. 0.8
Solution: RQ = CO2/O2 = 102/145 ≈ 0.7, typical of fats.
Q30 — Respiratory Balance Sheet & RQ · easy · theory
What is the RQ if proteins are used as respiratory substrate?
A. 0.9 ✓ Correct
B. 1
C. 0.7
D. 0.8
Solution: Proteins have an RQ of about 0.9.