CBSE Class 11 Biology – Photosynthesis in Higher Plants | Very Short Answer Questions with Answers (NCERT Based)

Course & Examination Details

Course: CBSE Class 11 Biology
Unit: Unit IV – Plant Physiology
Chapter: Chapter 13 – Photosynthesis in Higher Plants
Prescribed Textbook: NCERT
Board: CBSE

CBSE Board Examination Focus

• VSAs test definitions, principles, and key concepts
• Frequently asked in annual exams and unit tests
• Answers must be precise, NCERT-based, and to the point

Section A: Light Reaction (Questions 1–15)

Q1. What is photosynthesis?
Ans: Photosynthesis is the process by which green plants synthesize carbohydrates from carbon dioxide and water using light energy in the presence of chlorophyll.

Q2. Where does the light reaction occur?
Ans: Light reactions occur in the thylakoid membranes of chloroplasts, particularly in the grana regions of mesophyll cells.

Q3. Name the primary photosynthetic pigment.
Ans: Chlorophyll a is the primary photosynthetic pigment that directly participates in conversion of light energy into chemical energy.

Q4. What is a photosystem?
Ans: A photosystem is a pigment–protein complex in thylakoid membranes that absorbs light energy and initiates photochemical reactions.

Q5. Name the reaction centre of Photosystem II.
Ans: The reaction centre of Photosystem II is P680, which absorbs light at a wavelength of 680 nm.

Q6. Which photosystem is involved in photolysis of water?
Ans: Photosystem II is involved in photolysis of water, resulting in release of oxygen, protons, and electrons.

Q7. What is photolysis of water?
Ans: Photolysis of water is the light-driven splitting of water molecules into oxygen, protons, and electrons during photosynthesis.

Q8. Where does oxygen released during photosynthesis come from?
Ans: The oxygen released during photosynthesis comes from the splitting of water molecules during light reaction.

Q9. What is photophosphorylation?
Ans: Photophosphorylation is the synthesis of ATP from ADP and inorganic phosphate using light energy during photosynthesis.

Q10. Differentiate cyclic photophosphorylation briefly.
Ans: Cyclic photophosphorylation involves only Photosystem I and results in formation of ATP without production of NADPH or oxygen.

Q11. What is non-cyclic photophosphorylation?
Ans: Non-cyclic photophosphorylation involves both Photosystem II and I, producing ATP, NADPH, and oxygen.

Q12. Name the assimilatory powers of photosynthesis.
Ans: ATP and NADPH produced during light reactions are called assimilatory powers used in carbon fixation.

Q13. Which photosystem has reaction centre P700?
Ans: Photosystem I has the reaction centre P700, absorbing light of wavelength 700 nm.

Q14. What is the role of NADP⁺ in photosynthesis?
Ans: NADP⁺ acts as the final electron acceptor during light reaction and is reduced to NADPH.

Q15. Why are accessory pigments important?
Ans: Accessory pigments absorb light of different wavelengths and transfer energy to chlorophyll a, increasing photosynthetic efficiency.

Section B: Dark Reaction (Calvin Cycle) (Questions 16–25)

Q16. What is dark reaction?
Ans: Dark reaction is the light-independent phase of photosynthesis in which carbon dioxide is fixed into carbohydrates using ATP and NADPH.

Q17. Where does the Calvin cycle occur?
Ans: The Calvin cycle occurs in the stroma of chloroplasts in photosynthetic cells.

Q18. Name the enzyme involved in CO₂ fixation.
Ans: RuBisCO (Ribulose-1,5-bisphosphate carboxylase-oxygenase) is the enzyme responsible for CO₂ fixation.

Q19. What is the first stable product of Calvin cycle?
Ans: The first stable product of the Calvin cycle is 3-phosphoglyceric acid (3-PGA).

Q20. What is carboxylation?
Ans: Carboxylation is the initial step of Calvin cycle where CO₂ combines with RuBP in presence of RuBisCO.

Q21. Why is RuBisCO called a dual enzyme?
Ans: RuBisCO shows both carboxylase and oxygenase activities, leading to photosynthesis or photorespiration respectively.

Q22. What is regeneration phase of Calvin cycle?
Ans: Regeneration is the phase where RuBP is regenerated using ATP to continue the Calvin cycle.

Q23. Does dark reaction require light directly?
Ans: Dark reaction does not require light directly but depends on ATP and NADPH produced during light reaction.

Q24. Why is dark reaction also called biosynthetic phase?
Ans: Dark reaction synthesizes carbohydrates from carbon dioxide, hence it is called the biosynthetic phase.

Q25. How many CO₂ molecules are needed to form one glucose?
Ans: Six molecules of carbon dioxide are required to synthesize one molecule of glucose.

Section C: C₃ and C₄ Pathways (Questions 26–40)

Q26. What is C₃ pathway?
Ans: C₃ pathway is the Calvin cycle where the first stable product of CO₂ fixation is a three-carbon compound, 3-PGA.

Q27. Name two C₃ plants.
Ans: Wheat and rice are examples of C₃ plants where photosynthesis occurs mainly through Calvin cycle.

Q28. What is photorespiration?
Ans: Photorespiration is a wasteful process where RuBisCO binds oxygen, releasing CO₂ and reducing photosynthetic efficiency.

Q29. Why is photorespiration common in C₃ plants?
Ans: C₃ plants lack a CO₂-concentrating mechanism, so RuBisCO often reacts with oxygen at high temperature.

Q30. What is C₄ pathway?
Ans: C₄ pathway is an alternative photosynthetic pathway where the first stable product of CO₂ fixation is a four-carbon compound.

Q31. Name the first stable product of C₄ pathway.
Ans: Oxaloacetic acid (OAA) is the first stable product of the C₄ pathway.

Q32. Which enzyme fixes CO₂ in C₄ plants initially?
Ans: PEP carboxylase initially fixes CO₂ in C₄ plants and has high affinity for carbon dioxide.

Q33. Name two C₄ plants.
Ans: Maize and sugarcane are common examples of C₄ plants.

Q34. What is Kranz anatomy?
Ans: Kranz anatomy refers to special leaf anatomy in C₄ plants with mesophyll cells surrounding bundle sheath cells.

Q35. Where does Calvin cycle occur in C₄ plants?
Ans: In C₄ plants, the Calvin cycle occurs in the bundle sheath cells.

Q36. Why is photorespiration absent in C₄ plants?
Ans: C₄ plants concentrate CO₂ around RuBisCO, preventing oxygen binding and eliminating photorespiration.

Q37. Which plants are more efficient at high temperature?
Ans: C₄ plants are more efficient at high temperature and light intensity than C₃ plants.

Q38. What is the primary CO₂ acceptor in C₃ plants?
Ans: Ribulose-1,5-bisphosphate (RuBP) is the primary CO₂ acceptor in C₃ plants.

Q39. Name the pathway discovered by Hatch and Slack.
Ans: The C₄ pathway is also known as the Hatch and Slack pathway.

Q40. Which pathway requires more ATP?
Ans: The C₄ pathway requires more ATP than the C₃ pathway due to additional steps.

Section D: Factors Affecting Photosynthesis (Questions 41–50)

Q41. Name two external factors affecting photosynthesis.
Ans: Light intensity and carbon dioxide concentration are important external factors affecting photosynthesis.

Q42. How does light intensity affect photosynthesis?
Ans: Increase in light intensity increases photosynthesis up to a saturation point beyond which the rate becomes constant.

Q43. Which light is most effective for photosynthesis?
Ans: Red and blue light are most effective for photosynthesis.

Q44. How does carbon dioxide concentration affect photosynthesis?
Ans: Increase in carbon dioxide concentration increases photosynthesis until saturation level is reached.

Q45. What is the optimum temperature for photosynthesis?
Ans: The optimum temperature for photosynthesis is generally between 25°C and 35°C.

Q46. How does water deficiency affect photosynthesis?
Ans: Water deficiency causes stomatal closure, reducing CO₂ entry and lowering photosynthetic rate.

Q47. Name two internal factors affecting photosynthesis.
Ans: Chlorophyll content and leaf anatomy are important internal factors affecting photosynthesis.

Q48. What is Blackman’s law of limiting factors?
Ans: It states that the rate of photosynthesis is limited by the factor present in minimum amount.

Q49. Why is CO₂ usually the limiting factor?
Ans: Atmospheric CO₂ concentration is low compared to plant requirements, making it a common limiting factor.

Q50. Why is photosynthesis vital for life on Earth?
Ans: Photosynthesis provides food and oxygen, forming the base of all food chains and sustaining life on Earth.

Ideal For

• CBSE Class 11 Annual Examinations
• NCERT-based unit tests
• Rapid revision and concept reinforcement