MCQs on Photosynthesis

1. The primary pigment involved in photosynthesis is:

A. Chlorophyll b
B. Chlorophyll a
C. Carotene
D. Xanthophyll
Answer: B. Chlorophyll a

2. Photosynthesis occurs in which organelle of plant cells?
A. Mitochondria
B. Ribosome
C. Chloroplast
D. Nucleus
Answer: C. Chloroplast

3. The light reaction of photosynthesis takes place in the:
A. Stroma
B. Thylakoid membrane
C. Cytoplasm
D. Nucleus
Answer: B. Thylakoid membrane

4. The Calvin cycle occurs in the:
A. Thylakoid membrane
B. Grana
C. Stroma
D. Cytosol
Answer: C. Stroma

5. The main function of light reaction is to produce:
A. Glucose and oxygen
B. ATP and NADPH
C. CO₂ and water
D. Only oxygen
Answer: B. ATP and NADPH

6. Photolysis of water occurs in:
A. Photosystem I
B. Photosystem II
C. Calvin cycle
D. Stroma
Answer: B. Photosystem II

7. The enzyme responsible for carbon fixation in C₃ plants is:
A. PEP carboxylase
B. RuBisCO
C. ATP synthase
D. Catalase
Answer: B. RuBisCO

8. The first stable product of Calvin cycle is:
A. Glucose
B. 3-phosphoglyceric acid (3-PGA)
C. RuBP
D. Pyruvate
Answer: B. 3-phosphoglyceric acid

9. Which gas is released during photosynthesis?
A. CO₂
B. O₂
C. N₂
D. CH₄
Answer: B. O₂

10. C₄ plants are characterized by the presence of:
A. Only mesophyll cells
B. Kranz anatomy
C. No chloroplast
D. Only bundle sheath cells
Answer: B. Kranz anatomy

11. In photosynthesis, water acts as:
A. Electron donor
B. Electron acceptor
C. Catalyst
D. Product
Answer: A. Electron donor

12. Which wavelength of light is most effective in photosynthesis?
A. Green
B. Yellow
C. Blue and red
D. Infrared
Answer: C. Blue and red

13. The term “photorespiration” refers to:
A. Oxygen evolution
B. CO₂ fixation
C. Uptake of O₂ and release of CO₂ in light
D. ATP synthesis
Answer: C. Uptake of O₂ and release of CO₂ in light

14. The pigment that absorbs light energy and transfers it to chlorophyll a is:
A. Accessory pigment
B. Primary pigment
C. Enzyme
D. Protein
Answer: A. Accessory pigment

15. The ultimate source of oxygen released in photosynthesis is:
A. CO₂
B. Glucose
C. Water
D. Chlorophyll
Answer: C. Water

16. The process by which plants convert light energy into chemical energy is called:
A. Respiration
B. Transpiration
C. Photosynthesis
D. Fermentation
Answer: C. Photosynthesis

17. Which molecule is regenerated in the Calvin cycle?
A. Glucose
B. RuBP
C. NADPH
D. ATP
Answer: B. RuBP

18. C₄ pathway was first discovered by:
A. Calvin
B. Hatch and Slack
C. Blackman
D. Priestley
Answer: B. Hatch and Slack

19. CAM plants open their stomata during:
A. Day
B. Night
C. Both day and night
D. Afternoon only
Answer: B. Night

20. The Z-scheme in photosynthesis represents:
A. Calvin cycle
B. Electron transport pathway
C. Glycolysis
D. Krebs cycle
Answer: B. Electron transport pathway