CBSE Class 11 Biology – Respiration in Plants | Very Short Answer Questions with Answers (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 Focus

• VSAs test definitions, sites, steps, and key concepts
• Answers must be precise, factual, and NCERT-based
• Frequently asked in unit tests and annual examinations

Section A: Glycolysis (Questions 1–15)

Q1. What is respiration in plants?
Ans: Respiration in plants is the enzymatic oxidation of organic food to release energy in the form of ATP required for metabolic activities.

Q2. Where does glycolysis occur in plant cells?
Ans: Glycolysis occurs in the cytoplasm of plant cells and does not require oxygen.

Q3. Why is glycolysis called EMP pathway?
Ans: Glycolysis is called EMP pathway after Embden, Meyerhof, and Parnas, who described its reaction sequence.

Q4. What is the end product of glycolysis?
Ans: The end product of glycolysis is pyruvic acid, a three-carbon compound.

Q5. How many ATP molecules are consumed in glycolysis?
Ans: Two ATP molecules are consumed during the preparatory phase of glycolysis.

Q6. What is the net ATP gain in glycolysis?
Ans: The net gain of ATP in glycolysis is two ATP molecules per glucose molecule.

Q7. Name the reducing equivalents formed during glycolysis.
Ans: Two molecules of NADH are formed during glycolysis.

Q8. Is glycolysis aerobic or anaerobic?
Ans: Glycolysis is an anaerobic pathway as it does not require oxygen.

Q9. Which compound links glycolysis to Krebs cycle?
Ans: Acetyl-CoA links glycolysis to the Krebs cycle.

Q10. What happens to pyruvic acid under aerobic conditions?
Ans: Pyruvic acid enters mitochondria and is converted into acetyl-CoA for aerobic respiration.

Q11. What is substrate-level phosphorylation?
Ans: Substrate-level phosphorylation is direct ATP synthesis during glycolysis without involvement of electron transport chain.

Q12. How many pyruvate molecules are formed from one glucose?
Ans: Two molecules of pyruvic acid are formed from one glucose molecule.

Q13. Name one importance of glycolysis.
Ans: Glycolysis provides ATP and metabolic intermediates essential for cellular respiration and biosynthesis.

Q14. Does glycolysis occur in mitochondria?
Ans: No, glycolysis occurs in the cytoplasm, not in mitochondria.

Q15. Why is glycolysis considered a universal pathway?
Ans: Glycolysis occurs in all living organisms, both aerobic and anaerobic.

Section B: Krebs Cycle (Questions 16–30)

Q16. What is the Krebs cycle?
Ans: The Krebs cycle is a cyclic pathway in which acetyl-CoA is completely oxidised to carbon dioxide with energy release.

Q17. Where does the Krebs cycle occur?
Ans: The Krebs cycle occurs in the mitochondrial matrix.

Q18. What is the first stable compound of Krebs cycle?
Ans: Citric acid is the first stable compound formed in the Krebs cycle.

Q19. Which molecule combines with acetyl-CoA to form citrate?
Ans: Oxaloacetic acid combines with acetyl-CoA to form citrate.

Q20. How many CO₂ molecules are released per acetyl-CoA?
Ans: Two molecules of carbon dioxide are released per acetyl-CoA.

Q21. Name one reducing equivalent produced in Krebs cycle.
Ans: NADH is a reducing equivalent produced in the Krebs cycle.

Q22. How many NADH molecules are formed per acetyl-CoA?
Ans: Three NADH molecules are produced per acetyl-CoA.

Q23. How many FADH₂ molecules are formed per acetyl-CoA?
Ans: One FADH₂ molecule is formed per acetyl-CoA.

Q24. What is the ATP yield of Krebs cycle per turn?
Ans: One ATP molecule is produced per turn of the Krebs cycle.

Q25. Why is Krebs cycle called amphibolic?
Ans: It functions both in breakdown of molecules and supply of intermediates for biosynthesis.

Q26. Name a biosynthetic use of Krebs cycle intermediate.
Ans: Amino acids are synthesised using Krebs cycle intermediates.

Q27. Does Krebs cycle require oxygen directly?
Ans: Krebs cycle does not require oxygen directly but depends on oxygen for regeneration of NAD⁺ and FAD.

Q28. What happens if oxygen is absent during Krebs cycle?
Ans: Krebs cycle stops due to accumulation of reduced coenzymes.

Q29. Why is Krebs cycle important in respiration?
Ans: It releases energy-rich molecules and completes oxidation of glucose.

Q30. Which enzyme regulates entry of pyruvate into Krebs cycle?
Ans: Pyruvate dehydrogenase complex regulates conversion of pyruvate to acetyl-CoA.

Section C: Electron Transport System (Questions 31–40)

Q31. What is the electron transport system?
Ans: ETS is a series of electron carriers transferring electrons from NADH and FADH₂ to oxygen.

Q32. Where is ETS located in mitochondria?
Ans: ETS is located on the inner mitochondrial membrane or cristae.

Q33. What is the final electron acceptor in respiration?
Ans: Oxygen is the final electron acceptor in aerobic respiration.

Q34. What is oxidative phosphorylation?
Ans: Oxidative phosphorylation is ATP synthesis using energy released during electron transport.

Q35. Which process creates proton gradient in ETS?
Ans: Electron transport pumps protons across the inner mitochondrial membrane.

Q36. What enzyme synthesises ATP in ETS?
Ans: ATP synthase synthesises ATP using proton gradient energy.

Q37. How many ATP molecules are produced from one NADH?
Ans: Approximately three ATP molecules are produced from one NADH in plants.

Q38. What is the role of cytochromes?
Ans: Cytochromes transfer electrons during electron transport.

Q39. Why is ETS the major ATP-producing stage?
Ans: It uses energy of electron flow to generate maximum ATP.

Q40. What happens if ETS is blocked?
Ans: ATP synthesis stops, leading to energy deficiency in cells.

Section D: Fermentation & Respiratory Quotient (Questions 41–50)

Q41. What is fermentation?
Ans: Fermentation is anaerobic breakdown of glucose producing energy without oxygen.

Q42. Where does fermentation occur in cells?
Ans: Fermentation occurs in the cytoplasm.

Q43. Name one type of fermentation in plants.
Ans: Alcoholic fermentation occurs in plants and yeast.

Q44. What are the end products of alcoholic fermentation?
Ans: Ethanol, carbon dioxide, and energy are produced.

Q45. How much ATP is produced during fermentation?
Ans: Only two ATP molecules are produced per glucose molecule.

Q46. Why is fermentation less efficient?
Ans: Glucose is incompletely oxidised, releasing less energy.

Q47. What is respiratory quotient (RQ)?
Ans: RQ is the ratio of carbon dioxide evolved to oxygen consumed during respiration.

Q48. What is the RQ value for carbohydrates?
Ans: RQ value for carbohydrates is 1.

Q49. What does RQ indicate?
Ans: RQ indicates the type of respiratory substrate used.

Q50. Why is respiration essential for plants?
Ans: Respiration supplies ATP and intermediates required for growth, maintenance, and metabolism.

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