MCQs on Photosynthesis in Higher Plants – CBSE Class 11
MCQs on Photosynthesis in Higher Plants – CBSE Class 11 Biology (Unit IV | NCERT-Based)
CBSE Class 11 Biology – MCQs with Answers and Explanations
Unit IV: Plant Physiology
Topic: Photosynthesis in Higher Plants
Section A: Introduction & Pigments (Q1–Q10)
Q1. Photosynthesis is the process by which plants:
A. Release oxygen only
B. Convert light energy into chemical energy
C. Absorb minerals from soil
D. Respire in presence of light
Answer: B
Explanation: Photosynthesis converts light energy into chemical energy stored in carbohydrates.
Q2. The overall equation of photosynthesis was first given by:
A. Priestley
B. Ingenhousz
C. Sachs
D. Calvin
Answer: C
Explanation: Julius von Sachs proposed the overall chemical equation of photosynthesis.
Q3. Photosynthesis mainly occurs in:
A. Mitochondria
B. Nucleus
C. Chloroplast
D. Ribosome
Answer: C
Explanation: Chloroplasts contain pigments and enzymes necessary for photosynthesis.
Q4. The green colour of leaves is due to:
A. Carotene
B. Xanthophyll
C. Chlorophyll
D. Anthocyanin
Answer: C
Explanation: Chlorophyll reflects green light and absorbs red and blue light.
Q5. Which pigment absorbs maximum light energy?
A. Chlorophyll b
B. Chlorophyll a
C. Carotene
D. Xanthophyll
Answer: B
Explanation: Chlorophyll a is the primary pigment of photosynthesis.
Q6. Accessory pigments help in:
A. Releasing oxygen
B. Absorbing additional wavelengths
C. Fixing carbon dioxide
D. Synthesizing ATP
Answer: B
Explanation: Accessory pigments broaden the absorption spectrum.
Q7. Which pigment protects chlorophyll from photo-oxidation?
A. Chlorophyll a
B. Chlorophyll b
C. Carotenoids
D. Phycobilins
Answer: C
Explanation: Carotenoids prevent photo-oxidative damage.
Q8. The action spectrum of photosynthesis closely resembles the absorption spectrum of:
A. Chlorophyll a
B. Chlorophyll b
C. Carotenoids
D. All pigments combined
Answer: D
Explanation: Photosynthesis depends on all photosynthetic pigments.
Q9. Which wavelength of light is least effective in photosynthesis?
A. Blue
B. Red
C. Green
D. Violet
Answer: C
Explanation: Green light is mostly reflected, not absorbed.
Q10. Photosynthetic pigments are located in:
A. Stroma
B. Outer membrane
C. Thylakoid membrane
D. Inner membrane
Answer: C
Explanation: Pigments are embedded in thylakoid membranes.
Section B: Light Reaction (Q11–Q25)
Q11. Light reactions occur in:
A. Stroma
B. Thylakoid membrane
C. Cytoplasm
D. Mitochondria
Answer: B
Explanation: Light reactions take place on thylakoid membranes.
Q12. Light reaction is also known as:
A. Dark reaction
B. Calvin cycle
C. Photochemical phase
D. Biosynthetic phase
Answer: C
Explanation: Light reactions involve photochemical processes.
Q13. Photolysis of water occurs in:
A. Photosystem I
B. Photosystem II
C. Calvin cycle
D. Stroma
Answer: B
Explanation: Water splitting occurs in Photosystem II.
Q14. Photolysis of water releases:
A. CO₂
B. ATP
C. O₂, protons, electrons
D. NADPH
Answer: C
Explanation: Water splitting produces oxygen, protons, and electrons.
Q15. The oxygen released during photosynthesis comes from:
A. Carbon dioxide
B. Glucose
C. Water
D. Chlorophyll
Answer: C
Explanation: Oxygen is derived from water molecules.
Q16. Which photosystem has P680 as reaction centre?
A. PSI
B. PSII
C. Cytochrome complex
D. ATP synthase
Answer: B
Explanation: PSII has P680 chlorophyll.
Q17. Photosystem I has reaction centre:
A. P700
B. P680
C. P600
D. P720
Answer: A
Explanation: PSI contains P700 chlorophyll.
Q18. ATP synthesis in light reaction occurs by:
A. Oxidative phosphorylation
B. Substrate-level phosphorylation
C. Photophosphorylation
D. Chemiosmosis only
Answer: C
Explanation: Light-driven ATP formation is photophosphorylation.
Q19. Cyclic photophosphorylation produces:
A. ATP only
B. ATP and NADPH
C. NADPH only
D. ATP and O₂
Answer: A
Explanation: Cyclic flow generates ATP without NADPH or oxygen.
Q20. Non-cyclic photophosphorylation produces:
A. ATP only
B. NADPH only
C. ATP, NADPH, O₂
D. ATP and CO₂
Answer: C
Explanation: Non-cyclic pathway produces ATP, NADPH, and oxygen.
Q21. The electron transport chain is located in:
A. Stroma
B. Grana
C. Thylakoid membrane
D. Cytoplasm
Answer: C
Explanation: ETC is embedded in thylakoid membrane.
Q22. Proton gradient is built across:
A. Inner membrane
B. Outer membrane
C. Thylakoid membrane
D. Stroma
Answer: C
Explanation: Proton accumulation occurs across thylakoid membrane.
Q23. ATP synthase is also called:
A. CF₀–CF₁ complex
B. Rubisco
C. Cytochrome b₆f
D. Ferredoxin
Answer: A
Explanation: ATP synthase is the CF₀–CF₁ complex.
Q24. The final electron acceptor in non-cyclic photophosphorylation is:
A. Oxygen
B. NADP⁺
C. Chlorophyll
D. Water
Answer: B
Explanation: NADP⁺ accepts electrons to form NADPH.
Q25. Light reaction mainly provides:
A. Glucose
B. ATP and NADPH
C. CO₂
D. Starch
Answer: B
Explanation: ATP and NADPH are used in the Calvin cycle.
Section C: Dark Reaction (Calvin Cycle) (Q26–Q40)
Q26. Dark reaction occurs in:
A. Thylakoid
B. Grana
C. Stroma
D. Cytoplasm
Answer: C
Explanation: Calvin cycle occurs in chloroplast stroma.
Q27. Dark reaction does not require:
A. CO₂
B. ATP
C. NADPH
D. Light directly
Answer: D
Explanation: It is light-independent but depends on ATP and NADPH.
Q28. Calvin cycle was discovered by:
A. Sachs
B. Priestley
C. Calvin
D. Hill
Answer: C
Explanation: Melvin Calvin discovered the C₃ pathway.
Q29. The primary CO₂ acceptor in Calvin cycle is:
A. PEP
B. RuBP
C. PGA
D. PGAL
Answer: B
Explanation: Ribulose bisphosphate (RuBP) accepts CO₂.
Q30. The enzyme that fixes CO₂ is:
A. PEP carboxylase
B. Rubisco
C. ATP synthase
D. Ferredoxin
Answer: B
Explanation: Rubisco catalyzes CO₂ fixation.
Q31. The first stable product of Calvin cycle is:
A. RuBP
B. PGA
C. PGAL
D. Glucose
Answer: B
Explanation: 3-phosphoglyceric acid (PGA) is the first stable compound.
Q32. For synthesis of one glucose molecule, Calvin cycle requires:
A. 3 CO₂
B. 6 CO₂
C. 9 CO₂
D. 12 CO₂
Answer: B
Explanation: Six CO₂ molecules are required to form one glucose.
Q33. Reduction phase of Calvin cycle consumes:
A. ATP only
B. NADPH only
C. ATP and NADPH
D. CO₂ only
Answer: C
Explanation: Both ATP and NADPH are used.
Q34. Regeneration of RuBP requires:
A. NADPH
B. ATP
C. CO₂
D. Oxygen
Answer: B
Explanation: ATP is used to regenerate RuBP.
Q35. Which compound exits Calvin cycle to form sugars?
A. PGA
B. RuBP
C. PGAL
D. PEP
Answer: C
Explanation: PGAL (G3P) is used to synthesize glucose.
Q36. C₃ plants show maximum photosynthesis at:
A. High oxygen
B. High CO₂
C. Low CO₂
D. Darkness
Answer: B
Explanation: Higher CO₂ suppresses photorespiration.
Q37. Photorespiration occurs mainly in:
A. C₄ plants
B. CAM plants
C. C₃ plants
D. Algae
Answer: C
Explanation: Rubisco acts as oxygenase in C₃ plants.
Q38. Photorespiration results in:
A. Sugar formation
B. Loss of carbon
C. ATP production
D. Oxygen release
Answer: B
Explanation: Photorespiration causes carbon loss without ATP synthesis.
Q39. Which organelle is involved in photorespiration?
A. Chloroplast only
B. Chloroplast and mitochondria
C. Chloroplast, mitochondria, peroxisome
D. Cytoplasm
Answer: C
Explanation: Photorespiration involves three organelles.
Q40. Which enzyme initiates photorespiration?
A. PEP carboxylase
B. Rubisco (oxygenase activity)
C. ATP synthase
D. Ferredoxin
Answer: B
Explanation: Rubisco acts as oxygenase.
Section D: C₄ Pathway, CAM & Factors (Q41–Q50)
Q41. C₄ pathway was discovered by:
A. Calvin
B. Hatch and Slack
C. Sachs
D. Hill
Answer: B
Explanation: Hatch and Slack described the C₄ pathway.
Q42. The first stable compound in C₄ plants is:
A. PGA
B. RuBP
C. OAA
D. Malate
Answer: C
Explanation: Oxaloacetic acid (OAA) is the first product.
Q43. Primary CO₂ acceptor in C₄ plants is:
A. RuBP
B. PGA
C. PEP
D. PGAL
Answer: C
Explanation: PEP accepts CO₂ in mesophyll cells.
Q44. Bundle sheath cells lack:
A. Chloroplasts
B. Grana
C. Stroma
D. Mitochondria
Answer: B
Explanation: Bundle sheath chloroplasts are agranal.
Q45. C₄ plants show negligible photorespiration because:
A. Rubisco absent
B. High CO₂ concentration in bundle sheath
C. Low temperature
D. No oxygen
Answer: B
Explanation: CO₂ concentration suppresses oxygenase activity.
Q46. CAM plants fix CO₂ during:
A. Day only
B. Night only
C. Both day and night
D. Evening
Answer: B
Explanation: CAM plants fix CO₂ at night.
Q47. CAM plants keep stomata open during:
A. Day
B. Night
C. Noon
D. Evening
Answer: B
Explanation: Night opening reduces water loss.
Q48. Which factor does NOT affect photosynthesis?
A. Light
B. CO₂ concentration
C. Temperature
D. Soil texture
Answer: D
Explanation: Soil texture does not directly affect photosynthesis.
Q49. Blackman’s law of limiting factors states that:
A. All factors affect equally
B. Rate is controlled by the slowest factor
C. Light alone controls photosynthesis
D. Temperature is always limiting
Answer: B
Explanation: The limiting factor determines the rate.
Q50. Photosynthesis is vital because it:
A. Releases oxygen only
B. Produces food for plants only
C. Maintains CO₂ balance
D. Supports all life on Earth
Answer: D
Explanation: Photosynthesis forms the base of all food chains.