Chapter 14: Respiration in Plants – MCQs
π± Respiration in Plants – MCQs
Part 1: (Q1 β Q25)
Q1. Which one of the following is the first step in respiration?
a) Glycolysis
b) Krebs cycle
c) Electron transport chain
d) Fermentation
Answer: a) Glycolysis
π Glycolysis is the initial pathway of glucose breakdown, occurring in the cytoplasm.
Q2. Where does glycolysis occur in plant cells?
a) Nucleus
b) Cytoplasm
c) Mitochondria
d) Chloroplast
Answer: b) Cytoplasm
π Glycolysis takes place in the cytoplasm of both prokaryotic and eukaryotic cells.
Q3. The end product of glycolysis is:
a) Pyruvate
b) Acetyl CoA
c) Ethanol
d) COβ
Answer: a) Pyruvate
π Glycolysis converts glucose into two molecules of pyruvate with ATP and NADH formation.
Q4. Which of the following is an anaerobic process?
a) Krebs cycle
b) Electron transport chain
c) Glycolysis
d) Oxidative phosphorylation
Answer: c) Glycolysis
π Glycolysis does not require oxygen, though its products are further oxidized aerobically.
Q5. How many ATP molecules are gained (net) from one glucose molecule in glycolysis?
a) 2
b) 4
c) 6
d) 8
Answer: a) 2
π Although 4 ATP are produced, 2 are consumed, giving a net gain of 2 ATP.
Q6. In aerobic respiration, the link reaction connects:
a) Glycolysis and Fermentation
b) Glycolysis and Krebs cycle
c) Krebs cycle and ETC
d) Fermentation and ETC
Answer: b) Glycolysis and Krebs cycle
π Pyruvate from glycolysis is converted into Acetyl-CoA, linking glycolysis to the Krebs cycle.
Q7. The Krebs cycle occurs in:
a) Cytoplasm
b) Chloroplast
c) Mitochondrial matrix
d) Endoplasmic reticulum
Answer: c) Mitochondrial matrix
π All Krebs cycle enzymes are located in the mitochondrial matrix.
Q8. The first stable product of Krebs cycle is:
a) Oxaloacetate
b) Citrate
c) Succinate
d) Malate
Answer: b) Citrate
π Acetyl-CoA combines with oxaloacetate to form citrate.
Q9. How many ATP equivalents are produced per NADH during oxidative phosphorylation?
a) 1
b) 2
c) 2.5β3
d) 4
Answer: c) 2.5β3
π Each NADH yields about 2.5β3 ATP via the electron transport chain.
Q10. The final electron acceptor in aerobic respiration is:
a) NADβΊ
b) FAD
c) Oxygen
d) Water
Answer: c) Oxygen
π Oxygen accepts electrons at the end of the ETC, forming water.
Q11. Which of the following is not produced during the Krebs cycle?
a) ATP (or GTP)
b) NADH
c) FADHβ
d) Oxygen
Answer: d) Oxygen
π Oxygen is not produced but consumed in the ETC stage.
Q12. RQ (Respiratory Quotient) of glucose is:
a) 0.7
b) 1.0
c) >1
d) 0.5
Answer: b) 1.0
π Complete oxidation of carbohydrates yields equal amounts of COβ and Oβ.
Q13. RQ value less than 1 is characteristic of:
a) Carbohydrates
b) Fats
c) Organic acids
d) Proteins
Answer: b) Fats
π Fat oxidation consumes more oxygen, giving an RQ < 1.
Q14. Which pathway produces both NADPH and ATP?
a) Glycolysis
b) Pentose phosphate pathway
c) Krebs cycle
d) ETC
Answer: b) Pentose phosphate pathway
π PPP generates NADPH and metabolic intermediates, useful for biosynthesis.
Q15. In alcoholic fermentation, the final product is:
a) Lactic acid
b) Ethanol + COβ
c) Pyruvate
d) Acetyl CoA
Answer: b) Ethanol + COβ
π Yeast and some plant tissues convert pyruvate to ethanol and COβ anaerobically.
Q16. Which enzyme converts pyruvate to acetyl-CoA?
a) Pyruvate kinase
b) Pyruvate dehydrogenase
c) Lactate dehydrogenase
d) Alcohol dehydrogenase
Answer: b) Pyruvate dehydrogenase
π Pyruvate dehydrogenase complex catalyzes oxidative decarboxylation of pyruvate.
Q17. Number of ATP formed per glucose in aerobic respiration (in eukaryotes):
a) 18
b) 28
c) 30β32
d) 36β38
Answer: c) 30β32
π Modern estimates: ~30β32 ATP per glucose molecule, varying by conditions.
Q18. Pasteur effect refers to:
a) Inhibition of glycolysis by oxygen
b) Increase in fermentation in absence of Oβ
c) Formation of ATP in glycolysis
d) Role of NADH in respiration
Answer: a) Inhibition of glycolysis by oxygen
π Presence of Oβ shifts metabolism to oxidative phosphorylation, reducing fermentation.
Q19. The enzyme hexokinase catalyzes:
a) Glucose β Glucose-6-phosphate
b) Pyruvate β Lactate
c) Acetyl CoA β Citrate
d) Fumarate β Malate
Answer: a) Glucose β Glucose-6-phosphate
π Hexokinase phosphorylates glucose in the first step of glycolysis.
Q20. Anaerobic respiration produces energy:
a) More than aerobic
b) Less than aerobic
c) Equal to aerobic
d) None
Answer: b) Less than aerobic
π Anaerobic pathways yield only 2 ATP/glucose, while aerobic respiration yields ~30.
Q21. Which substrate shows highest RQ (>1)?
a) Carbohydrates
b) Fats
c) Proteins
d) Organic acids
Answer: d) Organic acids
π Oxidation of organic acids releases more COβ compared to Oβ consumed, RQ > 1.
Q22. Which process does not occur in mitochondria?
a) Krebs cycle
b) ETC
c) Glycolysis
d) Oxidative phosphorylation
Answer: c) Glycolysis
π Glycolysis occurs in cytoplasm, while the rest are mitochondrial processes.
Q23. In plants, alternative oxidase pathway is located in:
a) Cytoplasm
b) Chloroplast
c) Mitochondria
d) Peroxisome
Answer: c) Mitochondria
π Alternative oxidase (AOX) bypasses the ETC in plant mitochondria.
Q24. Which intermediate links glycolysis to TCA cycle?
a) Acetyl-CoA
b) Citrate
c) Malate
d) Succinate
Answer: a) Acetyl-CoA
π Pyruvate is converted to Acetyl-CoA before entering the Krebs cycle.
Q25. The net gain of ATP during anaerobic respiration in plants is:
a) 2
b) 4
c) 30
d) 36
Answer: a) 2
π Only glycolysis contributes ATP during anaerobic respiration.
π± Plant Physiology β Respiration in Plants (MCQs with Answers & Explanations)
Part 2: (Q26 β Q50)
Q26. Which one of the following is an amphibolic pathway?
a) Glycolysis
b) Krebs cycle
c) Fermentation
d) Photosynthesis
Answer: b) Krebs cycle
π Krebs cycle is both catabolic (breaks down acetyl-CoA) and anabolic (provides precursors for biosynthesis).
Q27. Which of the following is not an intermediate of the Krebs cycle?
a) Malate
b) Fumarate
c) Citrate
d) Pyruvate
Answer: d) Pyruvate
π Pyruvate enters mitochondria but is not part of the Krebs cycle itself.
Q28. In electron transport chain (ETC), ATP synthesis occurs by:
a) Substrate level phosphorylation
b) Oxidative phosphorylation
c) Photophosphorylation
d) Direct phosphorylation
Answer: b) Oxidative phosphorylation
π ATP is synthesized by chemiosmosis using proton motive force generated in ETC.
Q29. Which complex of ETC transfers electrons from NADH to ubiquinone?
a) Complex I
b) Complex II
c) Complex III
d) Complex IV
Answer: a) Complex I
π NADH dehydrogenase (Complex I) transfers electrons from NADH to ubiquinone (CoQ).
Q30. FADHβ donates its electrons to ETC at:
a) Complex I
b) Complex II
c) Complex III
d) Complex IV
Answer: b) Complex II
π Succinate dehydrogenase (Complex II) transfers electrons from FADHβ to ubiquinone.
Q31. How many ATP are generated from complete oxidation of one molecule of FADHβ?
a) 1
b) 2
c) 1.5β2
d) 3
Answer: c) 1.5β2
π Each FADHβ yields ~1.5β2 ATP through the ETC.
Q32. The enzyme ATP synthase is located in:
a) Outer mitochondrial membrane
b) Inner mitochondrial membrane
c) Matrix
d) Cytoplasm
Answer: b) Inner mitochondrial membrane
π ATP synthase spans the inner mitochondrial membrane, using proton gradient to generate ATP.
Q33. Which step of glycolysis directly produces ATP?
a) Glucose β Glucose-6-phosphate
b) Phosphoenolpyruvate β Pyruvate
c) Fructose-6-phosphate β Fructose-1,6-bisphosphate
d) Pyruvate β Acetyl-CoA
Answer: b) Phosphoenolpyruvate β Pyruvate
π This step, catalyzed by pyruvate kinase, generates ATP via substrate-level phosphorylation.
Q34. Which substrate has RQ equal to 0.7?
a) Carbohydrates
b) Fats
c) Proteins
d) Organic acids
Answer: b) Fats
π Fat oxidation consumes more oxygen, leading to an RQ of 0.7.
Q35. In lactic acid fermentation, pyruvate is reduced to:
a) Acetyl-CoA
b) Lactate
c) Ethanol
d) Oxaloacetate
Answer: b) Lactate
π In muscle cells and some microbes, pyruvate is converted to lactate under anaerobic conditions.
Q36. The enzyme involved in ethanol production during fermentation is:
a) Alcohol dehydrogenase
b) Pyruvate dehydrogenase
c) Pyruvate kinase
d) Succinate dehydrogenase
Answer: a) Alcohol dehydrogenase
π Converts acetaldehyde to ethanol in yeast and some plant tissues.
Q37. How many COβ molecules are released during complete oxidation of one glucose in aerobic respiration?
a) 4
b) 6
c) 2
d) 8
Answer: b) 6
π 2 from pyruvate oxidation + 4 from Krebs cycle = 6 COβ molecules.
Q38. The enzyme responsible for substrate-level phosphorylation in Krebs cycle is:
a) Succinate dehydrogenase
b) Succinyl-CoA synthetase
c) Malate dehydrogenase
d) Fumarase
Answer: b) Succinyl-CoA synthetase
π Catalyzes conversion of succinyl-CoA to succinate, generating GTP/ATP.
Q39. Which of the following does not take place in the mitochondrial matrix?
a) Krebs cycle
b) Fatty acid oxidation
c) Glycolysis
d) Pyruvate decarboxylation
Answer: c) Glycolysis
π Glycolysis is exclusively cytoplasmic.
Q40. The enzyme that catalyzes conversion of phosphoenolpyruvate (PEP) to oxaloacetate in C4 plants also participates in respiration. It is:
a) PEP carboxylase
b) Pyruvate kinase
c) Malate dehydrogenase
d) Citrate synthase
Answer: a) PEP carboxylase
π It fixes COβ to PEP in photosynthesis and also plays role in metabolic anaplerosis.
Q41. How many NADH are formed per glucose molecule in glycolysis?
a) 1
b) 2
c) 3
d) 4
Answer: b) 2
π Each glucose produces 2 NADH in glycolysis.
Q42. The enzyme lactate dehydrogenase is involved in:
a) Glycolysis
b) Lactic acid fermentation
c) Krebs cycle
d) ETC
Answer: b) Lactic acid fermentation
π It reduces pyruvate to lactate using NADH.
Q43. Which of the following is an example of substrate-level phosphorylation?
a) ATP synthesis by ATP synthase
b) ATP generation during glycolysis
c) ATP production in ETC
d) ATP generation during photosynthesis
Answer: b) ATP generation during glycolysis
π Direct transfer of phosphate to ADP in glycolysis and Krebs cycle is substrate-level phosphorylation.
Q44. Oxidative decarboxylation of pyruvate produces:
a) Lactate
b) Acetyl-CoA, COβ, NADH
c) Ethanol
d) Oxaloacetate
Answer: b) Acetyl-CoA, COβ, NADH
π Pyruvate dehydrogenase converts pyruvate into acetyl-CoA with release of COβ and NADH.
Q45. Which of the following best explains why fats yield more ATP than carbohydrates?
a) They have higher water content
b) They are more reduced molecules
c) They are insoluble in water
d) They do not undergo glycolysis
Answer: b) They are more reduced molecules
π Fats have more CβH bonds, yielding more reducing equivalents (NADH, FADHβ).
Q46. Respiratory quotient (RQ) for proteins is approximately:
a) 0.7
b) 1.0
c) 0.8
d) >1
Answer: c) 0.8
π Protein metabolism gives an RQ of about 0.8 due to partial oxidation.
Q47. Which of the following is not a product of anaerobic respiration?
a) Ethanol
b) Lactate
c) COβ
d) Acetyl-CoA
Answer: d) Acetyl-CoA
π Acetyl-CoA is produced in aerobic respiration, not during fermentation.
Q48. Which process is directly linked to the proton gradient in mitochondria?
a) Glycolysis
b) Krebs cycle
c) ATP synthesis
d) Fermentation
Answer: c) ATP synthesis
π The proton gradient across the inner mitochondrial membrane drives ATP synthase.
Q49. Which is the universal hydrogen acceptor in respiration?
a) NADβΊ
b) FAD
c) Oxygen
d) ATP
Answer: a) NADβΊ
π NADβΊ accepts hydrogen/electrons during glycolysis and Krebs cycle.
Q50. In cyanide poisoning, which part of respiration is inhibited?
a) Glycolysis
b) Krebs cycle
c) Electron transport chain
d) Fermentation
Answer: c) Electron transport chain
π Cyanide blocks cytochrome oxidase (Complex IV), preventing electron transfer to Oβ.
π± Plant Physiology β Respiration in Plants (MCQs with Answers & Explanations)
Part 3: (Q51 β Q75)
Q51. Which of the following is a common intermediate of respiration and photosynthesis?
a) Pyruvate
b) Acetyl-CoA
c) Glyceraldehyde-3-phosphate (G3P)
d) Succinate
Answer: c) Glyceraldehyde-3-phosphate (G3P)
π G3P is formed in both glycolysis and Calvin cycle, linking respiration and photosynthesis.
Q52. During respiration, ATP formed directly in glycolysis and Krebs cycle is called:
a) Oxidative phosphorylation
b) Photophosphorylation
c) Substrate-level phosphorylation
d) Chemiosmosis
Answer: c) Substrate-level phosphorylation
π ATP formed by direct transfer of phosphate group from substrate to ADP.
Q53. The enzyme succinate dehydrogenase is unique because it is located in:
a) Mitochondrial matrix
b) Inner mitochondrial membrane
c) Cytoplasm
d) Outer mitochondrial membrane
Answer: b) Inner mitochondrial membrane
π Unlike other TCA cycle enzymes, succinate dehydrogenase is embedded in inner membrane (Complex II).
Q54. In plants, cyanide-resistant respiration occurs via:
a) Glycolysis
b) Alternative oxidase (AOX) pathway
c) Fermentation
d) Glyoxylate cycle
Answer: b) Alternative oxidase (AOX) pathway
π AOX in mitochondria allows electron transport to continue even in the presence of cyanide.
Q55. Respiratory quotient (RQ) of oxalic acid is:
a) 0.7
b) 1.0
c) >1
d) 0.5
Answer: c) >1
π Oxidation of organic acids like oxalic acid releases more COβ than Oβ consumed.
Q56. How many molecules of NADH are produced in one turn of Krebs cycle?
a) 2
b) 3
c) 4
d) 5
Answer: b) 3
π Each acetyl-CoA produces 3 NADH in one turn of the cycle.
Q57. The primary function of fermentation is to:
a) Generate more ATP than respiration
b) Reoxidize NADH to NADβΊ
c) Produce oxygen
d) Break down fatty acids
Answer: b) Reoxidize NADH to NADβΊ
π Fermentation ensures continuous glycolysis by regenerating NADβΊ.
Q58. Which compound enters the Krebs cycle directly?
a) Pyruvate
b) Acetyl-CoA
c) Lactate
d) Ethanol
Answer: b) Acetyl-CoA
π Pyruvate is converted to acetyl-CoA, which then enters the cycle.
Q59. In mitochondrial ETC, protons are pumped into:
a) Matrix
b) Cytoplasm
c) Intermembrane space
d) Nucleus
Answer: c) Intermembrane space
π Proton gradient builds up across the inner mitochondrial membrane, driving ATP synthesis.
Q60. The conversion of glucose to glucose-6-phosphate consumes:
a) NADH
b) ATP
c) FADHβ
d) COβ
Answer: b) ATP
π Hexokinase phosphorylates glucose using ATP as phosphate donor.
Q61. Which is the first step of the Krebs cycle?
a) Citrate β Isocitrate
b) Acetyl-CoA + Oxaloacetate β Citrate
c) Fumarate β Malate
d) Succinate β Fumarate
Answer: b) Acetyl-CoA + Oxaloacetate β Citrate
π Catalyzed by citrate synthase, forming 6C citrate from 4C oxaloacetate + 2C acetyl-CoA.
Q62. Which of the following is a shuttle system for transferring NADH from cytoplasm into mitochondria?
a) Malate-aspartate shuttle
b) Phosphate shuttle
c) Proton shuttle
d) Ubiquinone shuttle
Answer: a) Malate-aspartate shuttle
π Transfers reducing equivalents of cytosolic NADH into mitochondria.
Q63. Which process is inhibited by oligomycin?
a) Glycolysis
b) Krebs cycle
c) ATP synthase activity
d) Electron transport chain
Answer: c) ATP synthase activity
π Oligomycin blocks proton channel of ATP synthase, inhibiting ATP production.
Q64. Respiratory substrate yielding maximum energy is:
a) Glucose
b) Proteins
c) Fats
d) Organic acids
Answer: c) Fats
π Fats produce the most ATP (about 2.5 times more than carbohydrates).
Q65. The number of ATP generated in one turn of Krebs cycle (per acetyl-CoA) is approximately:
a) 6
b) 8
c) 10
d) 12
Answer: c) 10
π 3 NADH (~7.5 ATP) + 1 FADHβ (~1.5 ATP) + 1 ATP (substrate level) β 10 ATP.
Q66. Which of the following organisms can perform alcoholic fermentation?
a) Humans
b) Yeast
c) Green algae
d) Amoeba
Answer: b) Yeast
π Yeast ferments sugars to ethanol and COβ.
Q67. Which of the following steps releases COβ in respiration?
a) Glucose β Glucose-6-phosphate
b) Pyruvate β Acetyl-CoA
c) Malate β Oxaloacetate
d) Succinate β Fumarate
Answer: b) Pyruvate β Acetyl-CoA
π Oxidative decarboxylation releases COβ. Also seen in isocitrate β Ξ±-ketoglutarate and Ξ±-ketoglutarate β succinyl-CoA.
Q68. In aerobic respiration, how many oxygen molecules are required to completely oxidize one glucose molecule?
a) 3
b) 6
c) 8
d) 12
Answer: b) 6
π CβHββOβ + 6Oβ β 6COβ + 6HβO + Energy.
Q69. Which enzyme catalyzes the last step of glycolysis?
a) Hexokinase
b) Enolase
c) Pyruvate kinase
d) Aldolase
Answer: c) Pyruvate kinase
π Converts phosphoenolpyruvate to pyruvate, producing ATP.
Q70. The oxidative phosphorylation theory was proposed by:
a) Calvin
b) Peter Mitchell
c) Krebs
d) Pasteur
Answer: b) Peter Mitchell
π He proposed chemiosmotic theory, explaining ATP synthesis via proton gradient.
Q71. Which of the following is a high-energy compound?
a) ATP
b) NADβΊ
c) FAD
d) COβ
Answer: a) ATP
π ATP stores energy in its terminal phosphate bonds.
Q72. In mitochondria, ATP synthesis is coupled with:
a) Substrate-level phosphorylation
b) Proton gradient
c) Glycolysis
d) Fermentation
Answer: b) Proton gradient
π Chemiosmotic hypothesis states that proton motive force drives ATP synthesis.
Q73. Anaerobic respiration in muscles during intense exercise produces:
a) COβ + Ethanol
b) Lactic acid
c) Pyruvate
d) Acetyl-CoA
Answer: b) Lactic acid
π Muscle cells undergo lactic acid fermentation under oxygen deficiency.
Q74. Which enzyme catalyzes conversion of fumarate to malate?
a) Fumarase
b) Malate dehydrogenase
c) Succinyl-CoA synthetase
d) Citrate synthase
Answer: a) Fumarase
π Hydrates fumarate to malate in Krebs cycle.
Q75. Number of ATP molecules directly synthesized (substrate-level phosphorylation) in one glycolysis cycle is:
a) 2
b) 4
c) 6
d) 8
Answer: b) 4
π 2 ATP from 1,3-bisphosphoglycerate β 3-phosphoglycerate & 2 ATP from PEP β pyruvate. Net gain is 2 ATP because 2 are consumed earlier.
π± Plant Physiology β Respiration in Plants (MCQs with Answers & Explanations)
Part 4: (Q76 β Q100)
Q76. The process of respiration is essentially a:
a) Catabolic process
b) Anabolic process
c) Amphibolic process
d) None
Answer: a) Catabolic process
π Respiration breaks down organic substrates to release energy (ATP).
Q77. Which molecule acts as the universal energy currency of cells?
a) NADH
b) FADHβ
c) ATP
d) GTP
Answer: c) ATP
π ATP is used for most cellular energy-requiring processes.
Q78. The TCA cycle is also known as:
a) Calvin cycle
b) Krebs cycle
c) Hatch-Slack cycle
d) Glyoxylate cycle
Answer: b) Krebs cycle
π Also called citric acid cycle, discovered by Hans Krebs.
Q79. Which step in glycolysis produces NADH?
a) Glucose β Glucose-6-phosphate
b) Fructose-1,6-bisphosphate β G3P + DHAP
c) G3P β 1,3-bisphosphoglycerate
d) PEP β Pyruvate
Answer: c) G3P β 1,3-bisphosphoglycerate
π Catalyzed by glyceraldehyde-3-phosphate dehydrogenase, generating NADH.
Q80. Which of the following is not a respiratory substrate?
a) Glucose
b) Amino acids
c) Fatty acids
d) Cellulose
Answer: d) Cellulose
π Cellulose cannot be directly used as a respiratory substrate in most organisms.
Q81. In oxidative phosphorylation, coupling factor is:
a) FAD
b) Cytochrome c
c) ATP synthase
d) NADH
Answer: c) ATP synthase
π ATP synthase couples proton gradient to ATP synthesis.
Q82. Which statement about glycolysis is incorrect?
a) Occurs in cytoplasm
b) Requires oxygen
c) Produces pyruvate
d) Produces ATP
Answer: b) Requires oxygen
π Glycolysis is anaerobic and does not require oxygen.
Q83. In aerobic respiration, maximum ATP is formed in:
a) Glycolysis
b) Krebs cycle
c) Electron transport chain
d) Fermentation
Answer: c) Electron transport chain
π ETC + oxidative phosphorylation yield majority of ATP (~26β28).
Q84. Which of the following is an intermediate of both TCA cycle and amino acid metabolism?
a) Citrate
b) Ξ±-Ketoglutarate
c) Fumarate
d) Malate
Answer: b) Ξ±-Ketoglutarate
π Serves as precursor for amino acid (glutamate) synthesis.
Q85. Which enzyme converts isocitrate to Ξ±-ketoglutarate in Krebs cycle?
a) Isocitrate dehydrogenase
b) Malate dehydrogenase
c) Citrate synthase
d) Fumarase
Answer: a) Isocitrate dehydrogenase
π Catalyzes oxidative decarboxylation producing COβ and NADH.
Q86. How many molecules of ATP are produced from one molecule of glucose by fermentation?
a) 1
b) 2
c) 4
d) 6
Answer: b) 2
π Only glycolysis contributes ATP during fermentation.
Q87. The respiratory quotient of proteins is close to:
a) 0.7
b) 1.0
c) 0.8
d) >1
Answer: c) 0.8
π Due to incomplete oxidation, proteins give RQ around 0.8.
Q88. Which of the following occurs both in respiration and photosynthesis?
a) NADPH production
b) Electron transport chain
c) Fermentation
d) Glycolysis
Answer: b) Electron transport chain
π Both involve ETC and proton gradient-based ATP synthesis.
Q89. The glyoxylate cycle differs from Krebs cycle because it:
a) Produces more ATP
b) Bypasses COβ-releasing steps
c) Occurs in cytoplasm
d) Uses glucose directly
Answer: b) Bypasses COβ-releasing steps
π Allows conversion of fats to carbohydrates in plants.
Q90. The link between glycolysis and Krebs cycle is:
a) NADH
b) Acetyl-CoA
c) ATP
d) Pyruvate kinase
Answer: b) Acetyl-CoA
π Pyruvate is converted into acetyl-CoA before entering Krebs cycle.
Q91. During aerobic respiration, water is produced at which stage?
a) Glycolysis
b) Krebs cycle
c) Electron transport chain
d) Fermentation
Answer: c) Electron transport chain
π Oxygen accepts electrons and protons at the end of ETC, forming water.
Q92. Which enzyme catalyzes the conversion of malate to oxaloacetate?
a) Malate dehydrogenase
b) Fumarase
c) Citrate synthase
d) Succinyl-CoA synthetase
Answer: a) Malate dehydrogenase
π Produces oxaloacetate and NADH.
Q93. ATP yield per glucose molecule in prokaryotes is higher than in eukaryotes because:
a) More efficient enzymes
b) No mitochondria β no transport loss
c) Faster glycolysis
d) No pyruvate formed
Answer: b) No mitochondria β no transport loss
π In prokaryotes, glycolysis and ETC occur in cytoplasm/plasma membrane, avoiding shuttle losses.
Q94. Anaerobic respiration in yeast is used in:
a) Yogurt production
b) Bread making
c) Vinegar production
d) Cheese ripening
Answer: b) Bread making
π COβ released causes dough to rise, ethanol evaporates on baking.
Q95. Which of the following is not a cytochrome in ETC?
a) Cyt b
b) Cyt c
c) Cyt a
d) Cyt k
Answer: d) Cyt k
π Cytochromes b, c, a, aβ are part of ETC, no βcyt k.β
Q96. In plants, mitochondria are mainly active:
a) During photosynthesis only
b) During respiration both day and night
c) Only at night
d) Only during fermentation
Answer: b) During respiration both day and night
π Mitochondria function continuously to provide ATP.
Q97. Which of the following is a terminal oxidase in mitochondrial ETC?
a) Cytochrome b
b) Cytochrome c
c) Cytochrome oxidase (a+aβ)
d) Succinate dehydrogenase
Answer: c) Cytochrome oxidase (a+aβ)
π Transfers electrons to oxygen, reducing it to water.
Q98. The site of EMP pathway (glycolysis) is:
a) Nucleus
b) Cytoplasm
c) Mitochondria
d) Ribosome
Answer: b) Cytoplasm
π Glycolysis (Embden-Meyerhof-Parnas pathway) occurs in cytoplasm.
Q99. Which process provides precursors for synthesis of amino acids, nucleotides, and porphyrins?
a) Glycolysis
b) Fermentation
c) Krebs cycle
d) Photosynthesis
Answer: c) Krebs cycle
π It provides intermediates like Ξ±-ketoglutarate, oxaloacetate, succinyl-CoA for biosynthesis.
Q100. Total ATP produced from one glucose in aerobic respiration in plants is:
a) 2
b) 18
c) 30β32
d) 36β38
Answer: c) 30β32
π In plants, complete oxidation of one glucose yields about 30β32 ATP.
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