Question Bank — Photosynthesis in Higher Plants

NCERT Class 11 Biology · Chapter 11 · CBSE Board Pattern

Class 11 Biology Chapter 11 Question Bank CBSE Board Pattern

QUESTION BANK

Photosynthesis in Higher Plants (NCERT Class 11)

Section A — MCQs (10 questions, 1 mark each)

  1. Which pigment is the chief pigment associated with photosynthesis?
    (a) Chlorophyll b
    (b) Chlorophyll a
    (c) Xanthophyll
    (d) Carotenoid

  2. The reaction centre of Photosystem II absorbs light at
    (a) 700 nm
    (b) 680 nm
    (c) 660 nm
    (d) 720 nm

  3. In the Z-scheme, the final electron acceptor is
    (a) NADP⁺
    (b) ADP
    (c) O₂
    (d) H₂O

  4. The first stable product of CO₂ fixation in C₃ plants is
    (a) Oxaloacetic acid
    (b) 3-phosphoglyceric acid
    (c) Ribulose bisphosphate
    (d) Phosphoenol pyruvate

  5. Kranz anatomy is a characteristic feature of
    (a) C₃ plants only
    (b) C₄ plants only
    (c) Both C₃ and C₄ plants
    (d) CAM plants

  6. Photorespiration does not occur in
    (a) C₃ plants
    (b) C₄ plants
    (c) Both C₃ and C₄ plants
    (d) Algae

  7. The enzyme RuBisCO catalyses
    (a) Only carboxylation
    (b) Only oxygenation
    (c) Both carboxylation and oxygenation
    (d) Photophosphorylation

  8. Splitting of water is associated with
    (a) PS I only
    (b) PS II only
    (c) Both PS I and PS II
    (d) Stroma

Assertion-Reason Questions

  1. Assertion (A): Chlorophyll a is the only pigment that can convert light energy into chemical energy.
    Reason (R): Accessory pigments transfer energy to chlorophyll a and also protect it from photo-oxidation.
    (a) Both A and R are true and R is the correct explanation of A.
    (b) Both A and R are true but R is not the correct explanation of A.
    (c) A is true but R is false.
    (d) A is false but R is true.

  2. Assertion (A): C₄ plants show higher productivity than C₃ plants under high light and high temperature conditions.
    Reason (R): C₄ plants lack photorespiration and have a mechanism to increase CO₂ concentration at the RuBisCO site.
    (a) Both A and R are true and R is the correct explanation of A.
    (b) Both A and R are true but R is not the correct explanation of A.
    (c) A is true but R is false.
    (d) A is false but R is true.

Section B — Very Short Answer (6 questions, 2 marks each)

  1. Name the two photosystems and state the wavelength at which their reaction centres absorb light.
  2. What is the role of accessory pigments in photosynthesis?
  3. Differentiate between cyclic and non-cyclic photophosphorylation (any two points).
  4. Why is the biosynthetic phase also called the dark reaction? Is the name appropriate?
  5. What is the primary CO₂ acceptor in C₄ plants and where is it located?
  6. State Blackman’s Law of Limiting Factors.

Section C — Short Answer (5 questions, 3 marks each)

  1. Describe the structure of a chloroplast with reference to the sites of light and dark reactions.
  2. Explain the chemiosmotic hypothesis for ATP synthesis in chloroplasts.
  3. Write the three stages of the Calvin cycle. How many ATP and NADPH molecules are required to synthesise one glucose molecule?
  4. What is photorespiration? Why does it not occur in C₄ plants?
  5. List any three differences between C₃ and C₄ plants with respect to anatomy and physiology.

Section D — Long Answer (3 questions, 5 marks each)

  1. Describe the Z-scheme of electron transport in light reaction with the help of a labelled diagram. Explain the formation of ATP and NADPH.
  2. Explain the Hatch and Slack pathway (C₄ pathway) in detail. How is it different from the Calvin cycle in terms of site and first product?
  3. Discuss the factors affecting the rate of photosynthesis. Explain why C₃ and C₄ plants respond differently to CO₂ concentration and temperature.

Section E — Case/Source-Based (2 questions, 4 marks each)

25. Case: In an experiment, a variegated leaf and a leaf partially covered with black paper were exposed to sunlight. After testing, starch was found only in the green, uncovered portions.

(a) What does this experiment prove about the role of chlorophyll?
(b) Name the scientist who first showed that sunlight is essential for the purification of air by plants.
(c) Why was starch not formed in the covered portion?
(d) How does this experiment support the fact that photosynthesis occurs only in green parts of the plant?

26. Case: Farmers growing tomatoes in greenhouses often enrich the atmosphere with CO₂ up to 0.05%. C₃ plants respond to this by showing increased photosynthetic rates, while C₄ plants saturate at lower CO₂ levels.

(a) Why do C₃ plants benefit more from CO₂ enrichment?
(b) At what approximate CO₂ concentration do C₄ plants reach saturation?
(c) Name the enzyme that has higher affinity for CO₂ in C₄ plants at the initial fixation step.
(d) How does increased CO₂ concentration affect photorespiration in C₃ plants?

▶ Answer Key Attempt all questions first,
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Section A

  1. (b) Chlorophyll a — 1 mark
  2. (b) 680 nm — 1 mark
  3. (a) NADP⁺ — 1 mark
  4. (b) 3-phosphoglyceric acid — 1 mark
  5. (b) C₄ plants only — 1 mark
  6. (b) C₄ plants — 1 mark
  7. (c) Both carboxylation and oxygenation — 1 mark
  8. (b) PS II only — 1 mark
  9. (b) Both true, R not explanation of A — 1 mark
  10. (a) Both true, R correct explanation — 1 mark

Section B

  1. PS I (P700), PS II (P680) — 1 mark each
  2. Absorb light of different wavelengths and transfer energy to chlorophyll a; protect from photo-oxidation — 1+1 mark
  3. Cyclic: only PS I, ATP only; Non-cyclic: both PS I & II, ATP + NADPH — 1+1 mark
  4. Does not require light directly but depends on ATP & NADPH; misnomer as it continues briefly after light is cut off — 1+1 mark
  5. PEP (phosphoenol pyruvate) in mesophyll cells — 1+1 mark
  6. Rate of a process is determined by the factor present at its lowest (sub-optimal) level — 2 marks

Section C

  1. Outer/inner membrane, grana (light reaction), stroma (dark reaction) — 1 mark each
  2. Proton gradient across thylakoid membrane → protons move through CF₀ → conformational change in CF₁ → ATP synthesis — 3 marks
  3. Carboxylation, reduction, regeneration; 18 ATP + 12 NADPH per glucose — 2+1 marks
  4. Oxygenase activity of RuBisCO; C₄ plants increase CO₂ concentration at RuBisCO site — 1+2 marks
  5. Any three valid differences (Kranz anatomy, first product, photorespiration, temperature optimum, etc.) — 1 mark each

Section D

  1. Labelled diagram of Z-scheme (PS II → ETC → PS I → NADP⁺) with explanation of water splitting, ATP & NADPH formation — diagram 2 marks + explanation 3 marks
  2. PEP carboxylase in mesophyll → OAA → bundle sheath → CO₂ release → Calvin cycle; differences in site and first product — 3+2 marks
  3. Light, CO₂, temperature, water; C₃ saturates at higher CO₂, lower temperature optimum; C₄ opposite — 2+3 marks

Section E

  1. (a) Chlorophyll is essential — 1 mark
    (b) Jan Ingenhousz — 1 mark
    (c) No light → no photosynthesis — 1 mark
    (d) Starch formed only in green uncovered parts — 1 mark

  2. (a) Current CO₂ level is limiting for C₃ plants — 1 mark
    (b) ~360 µl L⁻¹ — 1 mark
    (c) PEP carboxylase — 1 mark
    (d) Reduces photorespiration by favouring carboxylation — 1 mark

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All questions are answerable from the NCERT chapter text. Reviewed by GFIS faculty.