MCQ 21:
What is the role of the enzyme ATP synthase in photosynthesis?
A) Fixing carbon dioxide
B) Splitting water molecules
C) Synthesizing ATP
D) Converting glucose to starch
Answer: C) Synthesizing ATP
Explanation:
ATP synthase is an enzyme that synthesizes ATP from ADP and inorganic phosphate, using the proton gradient generated during the light-dependent reactions.
MCQ 22:
Which gas is primarily absorbed by plants during photosynthesis?
A) Oxygen
B) Nitrogen
C) Carbon dioxide
D) Hydrogen
Answer: C) Carbon dioxide
Explanation:
Plants absorb carbon dioxide from the atmosphere through stomata, which is essential for the photosynthesis process to produce glucose.
MCQ 23:
What is the primary product of the Calvin cycle?
A) Glucose
B) Oxygen
C) ATP
D) NADPH
Answer: A) Glucose
Explanation:
The primary output of the Calvin cycle is glucose, which is synthesized from carbon dioxide and the energy carriers ATP and NADPH produced in the light-dependent reactions.
MCQ 24:
Which of the following is a characteristic of light-dependent reactions?
A) They take place in the stroma.
B) They require light energy.
C) They produce glucose directly.
D) They occur in the absence of light.
Answer: B) They require light energy.
Explanation:
Light-dependent reactions occur in the thylakoid membranes of chloroplasts and require light energy to generate ATP and NADPH.
MCQ 25:
In C3 plants, photorespiration is a process that:
A) Enhances photosynthesis.
B) Reduces the efficiency of carbon fixation.
C) Occurs in the presence of high CO₂ levels.
D) Produces more glucose.
Answer: B) Reduces the efficiency of carbon fixation.
Explanation:
Photorespiration occurs when RuBisCO fixes oxygen instead of carbon dioxide, leading to reduced efficiency in carbon fixation in C3 plants.
MCQ 26:
Which of the following factors can limit the rate of photosynthesis?
A) Sufficient light and water
B) High carbon dioxide concentration
C) Extreme temperatures
D) All of the above
Answer: C) Extreme temperatures
Explanation:
While sufficient light and CO₂ can enhance photosynthesis, extreme temperatures can limit the process by denaturing enzymes involved in photosynthesis.
MCQ 27:
The primary light-absorbing pigments in photosynthesis are located in which part of the chloroplast?
A) Stroma
B) Thylakoid membranes
C) Inner membrane
D) Outer membrane
Answer: B) Thylakoid membranes
Explanation:
The thylakoid membranes contain chlorophyll and other pigments that capture light energy during the light-dependent reactions of photosynthesis.
MCQ 28:
What is the significance of the light-harvesting complexes in photosynthesis?
A) They store glucose.
B) They transport water.
C) They capture and transfer light energy to reaction centers.
D) They fix carbon dioxide.
Answer: C) They capture and transfer light energy to reaction centers.
Explanation:
Light-harvesting complexes contain various pigments that absorb light energy and funnel it to the reaction centers where photosynthesis begins.
MCQ 29:
In which part of the chloroplast does the Calvin cycle occur?
A) Thylakoid membranes
B) Outer membrane
C) Stroma
D) Granum
Answer: C) Stroma
Explanation:
The Calvin cycle occurs in the stroma of chloroplasts, where it uses ATP and NADPH produced in the light-dependent reactions to fix carbon dioxide.
MCQ 30:
Which of the following processes occurs in the thylakoid membrane?
A) ATP synthesis
B) Glucose synthesis
C) Carbon fixation
D) Oxygen release
Answer: A) ATP synthesis
Explanation:
ATP synthesis occurs in the thylakoid membrane during the light-dependent reactions through chemiosmosis facilitated by ATP synthase.
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