1. Which of the following plants is an example of a C3 plant?
A. Maize
B. Wheat
C. Sugarcane
D. Pineapple
Answer: B. Wheat
Explanation: Wheat is a typical C3 plant that performs photosynthesis through the Calvin cycle. The first stable product is a 3-carbon compound, 3-phosphoglycerate (3-PGA).
2. What is the primary site of photosynthesis in C3 plants?
A. Bundle sheath cells
B. Mesophyll cells
C. Epidermal cells
D. Guard cells
Answer: B. Mesophyll cells
Explanation: In C3 plants, photosynthesis occurs entirely in mesophyll cells as they lack the specialized anatomy seen in C4 plants.
3. The first stable compound formed in C4 plants is:
A. 3-Phosphoglycerate
B. Oxaloacetate
C. Pyruvate
D. Ribulose-1,5-bisphosphate
Answer: B. Oxaloacetate
Explanation: In C4 plants, CO2 is initially fixed into oxaloacetate (a 4-carbon compound) in mesophyll cells.
4. Which enzyme is responsible for CO2 fixation in C4 plants?
A. RuBisCO
B. PEP carboxylase
C. Pyruvate kinase
D. ATP synthase
Answer: B. PEP carboxylase
Explanation: Phosphoenolpyruvate (PEP) carboxylase fixes CO2 in mesophyll cells of C4 plants, forming oxaloacetate.
5. The special leaf anatomy in C4 plants is termed as:
A. Kranz anatomy
B. Bundle sheath anatomy
C. Vascular bundle system
D. Mesophyll anatomy
Answer: A. Kranz anatomy
Explanation: C4 plants have Kranz anatomy, characterized by distinct bundle sheath cells surrounding vascular bundles.
6. CAM plants are adapted to:
A. High light conditions
B. Saline environments
C. Desert environments
D. Tropical climates
Answer: C. Desert environments
Explanation: CAM plants are adapted to arid conditions by fixing CO2 at night to minimize water loss during the day.
7. In CAM plants, CO2 fixation occurs:
A. Only in mesophyll cells during the day
B. Only at night in mesophyll cells
C. In bundle sheath cells during the day
D. At night in bundle sheath cells
Answer: B. Only at night in mesophyll cells
Explanation: CAM plants fix CO2 at night using PEP carboxylase to form malate, which is stored in vacuoles.
8. The Calvin cycle in CAM plants occurs during:
A. Night
B. Day
C. Both night and day
D. Only under water stress
Answer: B. Day
Explanation: CAM plants release CO2 from stored malate during the day for use in the Calvin cycle.
9. C4 photosynthesis is more efficient than C3 photosynthesis because:
A. It minimizes photorespiration
B. It occurs only at night
C. It uses more RuBisCO
D. It does not require ATP
Answer: A. It minimizes photorespiration
Explanation: C4 plants concentrate CO2 around RuBisCO, reducing oxygenation and minimizing photorespiration.
10. Which cells are absent in C3 plant leaves but present in C4 plants?
A. Epidermal cells
B. Bundle sheath cells
C. Mesophyll cells
D. Guard cells
Answer: B. Bundle sheath cells
Explanation: C3 plants lack the distinct bundle sheath cells that are present in C4 plants for photosynthesis.
11. CAM pathway is advantageous because it:
A. Reduces ATP usage
B. Minimizes water loss
C. Enhances protein synthesis
D. Increases oxygen absorption
Answer: B. Minimizes water loss
Explanation: CAM plants open stomata at night to reduce water loss while still capturing CO2.
12. In C3 plants, RuBisCO acts as:
A. Oxygenase only
B. Carboxylase only
C. Both carboxylase and oxygenase
D. Neither carboxylase nor oxygenase
Answer: C. Both carboxylase and oxygenase
Explanation: RuBisCO in C3 plants can fix CO2 (carboxylation) or O2 (oxygenation), leading to photorespiration.
13. In which plant group does spatial separation of CO2 fixation and the Calvin cycle occur?
A. C3 plants
B. C4 plants
C. CAM plants
D. Both C4 and CAM plants
Answer: B. C4 plants
Explanation: C4 plants separate CO2 fixation and the Calvin cycle between mesophyll and bundle sheath cells.
14. Temporal separation of CO2 fixation and the Calvin cycle is seen in:
A. C3 plants
B. C4 plants
C. CAM plants
D. Both C4 and CAM plants
Answer: C. CAM plants
Explanation: CAM plants fix CO2 at night and perform the Calvin cycle during the day.
15. The mesophyll cells in C4 plants lack:
A. RuBisCO
B. Chloroplasts
C. PEP carboxylase
D. Vacuoles
Answer: A. RuBisCO
Explanation: In C4 plants, mesophyll cells lack RuBisCO and instead contain PEP carboxylase for initial CO2 fixation.
16. The major disadvantage of C3 photosynthesis is:
A. Low ATP production
B. High photorespiration rates
C. Lack of RuBisCO
D. Absence of Calvin cycle
Answer: B. High photorespiration rates
Explanation: C3 plants face significant carbon loss due to oxygenation of RuBP by RuBisCO during photorespiration.
17. The stored form of carbon in CAM plants at night is:
A. Pyruvate
B. Malate
C. Oxaloacetate
D. 3-Phosphoglycerate
Answer: B. Malate
Explanation: CAM plants store malate in vacuoles at night after CO2 fixation by PEP carboxylase.
18. C4 plants are commonly found in:
A. Cold regions
B. Temperate regions
C. Tropical regions
D. Arid regions
Answer: C. Tropical regions
Explanation: C4 plants thrive in high-temperature environments due to their efficient photosynthetic mechanism.
19. Which of the following plants uses the CAM pathway?
A. Maize
B. Wheat
C. Pineapple
D. Rice
Answer: C. Pineapple
Explanation: Pineapple is a CAM plant adapted to arid conditions, fixing CO2 at night.
20. The primary carbon fixation enzyme in C3 plants is:
A. PEP carboxylase
B. RuBisCO
C. ATP synthase
D. NADP reductase
Answer: B. RuBisCO
Explanation: RuBisCO catalyzes the carboxylation of RuBP during the Calvin cycle in C3 plants.
