Chapter 14: Respiration in Plants – MCQs with Answers & Explanations
CBSE Class 11 Biology – Respiration in Plants | MCQs with Answers & Explanations (NCERT Based)
Course & Examination Details
Course: CBSE Class 11 Biology
Unit: Unit IV – Plant Physiology
Chapter: Chapter 14 – Respiration in Plants
Prescribed Textbook: NCERT
Board: CBSE
CBSE Board Examination Relevance
- MCQs assess conceptual clarity, sequence of reactions, and energy accounting
- Frequently asked in unit tests, term exams, and annual examinations
- All questions follow NCERT terminology, pathways, and values
Section A: Glycolysis (MCQs 1–15)
Q1. Respiration in plants is defined as:
A. Synthesis of food using light
B. Oxidation of glucose to release energy
C. Absorption of oxygen
D. Exchange of gases
Correct Answer: B
Explanation: Respiration involves enzymatic oxidation of organic food to release energy in the form of ATP.
Q2. Glycolysis occurs in the:
A. Mitochondria
B. Chloroplast
C. Cytoplasm
D. Nucleus
Correct Answer: C
Explanation: Glycolysis is a cytoplasmic pathway and does not require mitochondria.
Q3. Glycolysis is also known as:
A. TCA cycle
B. Calvin cycle
C. EMP pathway
D. ETS
Correct Answer: C
Explanation: It is called EMP pathway after Embden, Meyerhof, and Parnas.
Q4. End product of glycolysis is:
A. Acetyl-CoA
B. Citric acid
C. Pyruvic acid
D. Lactic acid
Correct Answer: C
Explanation: One glucose molecule produces two molecules of pyruvic acid.
Q5. Net ATP gain during glycolysis is:
A. 1
B. 2
C. 4
D. 6
Correct Answer: B
Explanation: Four ATP are formed and two are consumed, giving a net gain of two ATP.
Q6. Reducing equivalents formed during glycolysis are:
A. FADH₂
B. NADH
C. ATP
D. NADPH
Correct Answer: B
Explanation: Two NADH molecules are produced during oxidation steps of glycolysis.
Q7. Glycolysis is considered anaerobic because it:
A. Produces less ATP
B. Occurs in mitochondria
C. Does not require oxygen
D. Occurs only in anaerobes
Correct Answer: C
Q8. Substrate-level phosphorylation occurs during:
A. ETS only
B. Glycolysis only
C. Krebs cycle only
D. Glycolysis and Krebs cycle
Correct Answer: D
Explanation: Direct ATP formation occurs in both glycolysis and Krebs cycle.
Q9. How many pyruvate molecules are formed from one glucose?
A. 1
B. 2
C. 3
D. 4
Correct Answer: B
Q10. Which compound links glycolysis to Krebs cycle?
A. Pyruvate
B. Acetyl-CoA
C. Citric acid
D. Oxaloacetate
Correct Answer: B
Q11. Conversion of pyruvate to acetyl-CoA occurs in:
A. Cytoplasm
B. Chloroplast
C. Mitochondrial matrix
D. Cristae
Correct Answer: C
Q12. Which molecule is released during link reaction?
A. Oxygen
B. ATP
C. Carbon dioxide
D. Water
Correct Answer: C
Q13. Glycolysis is called a universal pathway because it:
A. Produces maximum ATP
B. Occurs only in plants
C. Occurs in all living organisms
D. Needs oxygen
Correct Answer: C
Q14. ATP produced directly in glycolysis is formed by:
A. Chemiosmosis
B. Oxidative phosphorylation
C. Substrate-level phosphorylation
D. Photophosphorylation
Correct Answer: C
Q15. Which of the following is NOT a product of glycolysis?
A. ATP
B. NADH
C. Pyruvate
D. FADH₂
Correct Answer: D
Section B: Krebs Cycle (MCQs 16–30)
Q16. Krebs cycle occurs in the:
A. Cytoplasm
B. Chloroplast
C. Mitochondrial matrix
D. Inner membrane
Correct Answer: C
Q17. The first stable compound of Krebs cycle is:
A. Oxaloacetic acid
B. Citric acid
C. Succinic acid
D. Malic acid
Correct Answer: B
Q18. Acetyl-CoA combines with ______ to form citrate.
A. Malate
B. Pyruvate
C. Oxaloacetate
D. Succinate
Correct Answer: C
Q19. Number of CO₂ molecules released per acetyl-CoA is:
A. 1
B. 2
C. 3
D. 4
Correct Answer: B
Q20. How many NADH molecules are produced per turn of Krebs cycle?
A. 1
B. 2
C. 3
D. 4
Correct Answer: C
Q21. One FADH₂ is produced during conversion of:
A. Citrate to isocitrate
B. Succinate to fumarate
C. Malate to oxaloacetate
D. Pyruvate to acetyl-CoA
Correct Answer: B
Q22. ATP produced per turn of Krebs cycle is:
A. 0
B. 1
C. 2
D. 3
Correct Answer: B
Q23. Krebs cycle is called amphibolic because it:
A. Produces ATP only
B. Uses oxygen directly
C. Has both anabolic and catabolic roles
D. Occurs in plants only
Correct Answer: C
Q24. Krebs cycle stops in absence of oxygen because:
A. Enzymes are absent
B. Acetyl-CoA is not formed
C. NAD⁺ and FAD are not regenerated
D. CO₂ is not released
Correct Answer: C
Q25. How many times does Krebs cycle operate per glucose molecule?
A. Once
B. Twice
C. Thrice
D. Four times
Correct Answer: B
Q26. Which pathway is called the central metabolic pathway?
A. Glycolysis
B. Fermentation
C. Krebs cycle
D. ETS
Correct Answer: C
Q27. Krebs cycle intermediates are used for synthesis of:
A. Amino acids
B. Fatty acids
C. Chlorophyll
D. All of the above
Correct Answer: D
Q28. Which step of respiration releases maximum CO₂?
A. Glycolysis
B. Link reaction
C. Krebs cycle
D. ETS
Correct Answer: C
Q29. Which enzyme complex converts pyruvate to acetyl-CoA?
A. ATP synthase
B. RuBisCO
C. Pyruvate dehydrogenase
D. Dehydrogenase
Correct Answer: C
Q30. Krebs cycle mainly produces:
A. ATP only
B. CO₂ only
C. Reduced coenzymes
D. Oxygen
Correct Answer: C
Section C: ETS, Fermentation & RQ (MCQs 31–50)
Q31. Electron transport system is located on:
A. Outer mitochondrial membrane
B. Inner mitochondrial membrane
C. Matrix
D. Cytoplasm
Correct Answer: B
Q32. Final electron acceptor in aerobic respiration is:
A. NAD⁺
B. FAD
C. Oxygen
D. Carbon dioxide
Correct Answer: C
Q33. ATP synthesis during ETS occurs by:
A. Substrate-level phosphorylation
B. Photophosphorylation
C. Oxidative phosphorylation
D. Glycolysis
Correct Answer: C
Q34. Proton gradient is essential for:
A. Glycolysis
B. Krebs cycle
C. Chemiosmosis
D. Fermentation
Correct Answer: C
Q35. Which enzyme synthesises ATP in mitochondria?
A. Dehydrogenase
B. ATP synthase
C. Cytochrome oxidase
D. Kinase
Correct Answer: B
Q36. Total ATP yield per glucose molecule in plants is approximately:
A. 2
B. 18
C. 36
D. 44
Correct Answer: C
Q37. Fermentation occurs in the:
A. Mitochondria
B. Chloroplast
C. Cytoplasm
D. Nucleus
Correct Answer: C
Q38. End products of alcoholic fermentation are:
A. Lactic acid and ATP
B. Ethanol and CO₂
C. CO₂ and water
D. Pyruvate and NADH
Correct Answer: B
Q39. ATP yield in fermentation per glucose is:
A. 1
B. 2
C. 4
D. 36
Correct Answer: B
Q40. Fermentation is less efficient because:
A. Oxygen is absent
B. ETS is inactive
C. Glucose is incompletely oxidised
D. ATP synthase is absent
Correct Answer: C
Q41. Respiratory quotient (RQ) is:
A. O₂ consumed / CO₂ released
B. CO₂ released / O₂ consumed
C. ATP produced / glucose used
D. Energy released / oxygen used
Correct Answer: B
Q42. RQ value for carbohydrates is:
A. 0.7
B. 1
C. >1
D. <1
Correct Answer: B
Q43. RQ value for fats is:
A. 1
B. Greater than 1
C. Less than 1
D. Zero
Correct Answer: C
Q44. RQ greater than 1 indicates respiration of:
A. Fats
B. Proteins
C. Organic acids
D. Carbohydrates
Correct Answer: C
Q45. Which process regenerates NAD⁺ during anaerobic respiration?
A. Glycolysis
B. ETS
C. Fermentation
D. Krebs cycle
Correct Answer: C
Q46. Respiration is called a stepwise process because:
A. All reactions occur at once
B. Energy is released gradually
C. Oxygen is used directly
D. ATP is formed first
Correct Answer: B
Q47. Which statement is correct about aerobic respiration?
A. Produces lactic acid
B. Produces ethanol
C. Produces maximum ATP
D. Occurs only in cytoplasm
Correct Answer: C
Q48. Which factor directly affects respiration rate?
A. Light
B. Temperature
C. Chlorophyll
D. Transpiration
Correct Answer: B
Q49. Respiration occurs:
A. Only in green tissues
B. Only during night
C. Only in leaves
D. In all living cells
Correct Answer: D
Q50. Respiration is essential because it:
A. Produces oxygen
B. Releases energy for life processes
C. Absorbs carbon dioxide
D. Synthesises glucose
Correct Answer: B
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