This section focuses on numerical and calculation-based problems related to the light and dark reactions of photosynthesis. It is designed for Class 11–12 students , NEET aspirants , and undergraduate learners who want to strengthen their quantitative understanding of photosynthetic processes.
In this section, you will practice:
Numericals based on ATP and NADPH requirement in the Calvin cycle
Calculations involving cyclic and non-cyclic photophosphorylation
Energy yield and efficiency-based problems
Stoichiometry of CO₂ fixation and carbohydrate formation
Comparison of energy balance in C3, C4, and CAM pathways
Graph-based numerical questions on light intensity and rate of photosynthesis
NCERT-aligned numerical problems and exam-oriented practice sets
The content is structured to improve step-by-step problem solving , enhance calculation accuracy , and help students confidently handle numerical questions in school exams, NEET, and undergraduate assessments .
Develop speed and precision in solving numerical applications related to light and dark reactions of photosynthesis.
Q. How many molecules of ATP are produced in the light-dependent reactions for each molecule of glucose synthesized?
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Solution
A total of 18 ATP molecules are produced for each glucose molecule synthesized.
Correct Answer:
A
— 18
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Q. How many molecules of ATP are produced in the light-dependent reactions for every molecule of glucose synthesized?
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Solution
A total of 36 ATP molecules are produced in the light-dependent reactions for every glucose molecule synthesized.
Correct Answer:
C
— 36
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Q. How many molecules of carbon dioxide are required to produce one molecule of glucose in the Calvin cycle?
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Solution
Six molecules of carbon dioxide are required to produce one molecule of glucose in the Calvin cycle.
Correct Answer:
D
— 6
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Q. In the absence of light, which process will cease in plants?
A.
Photosynthesis
B.
Respiration
C.
Transpiration
D.
Glycolysis
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Solution
Photosynthesis will cease in the absence of light, as it relies on light energy.
Correct Answer:
A
— Photosynthesis
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Q. In the light reactions of photosynthesis, which molecule is produced as a byproduct?
A.
Glucose
B.
Oxygen
C.
NADPH
D.
ATP
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Solution
Oxygen is produced as a byproduct during the light reactions of photosynthesis.
Correct Answer:
B
— Oxygen
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Q. What is the effect of increased light intensity on the rate of photosynthesis, assuming other factors are optimal?
A.
Decreases rate
B.
Increases rate
C.
No effect
D.
Stops photosynthesis
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Solution
Increased light intensity generally increases the rate of photosynthesis, up to a certain point.
Correct Answer:
B
— Increases rate
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Q. What is the effect of increased light intensity on the rate of photosynthesis, assuming other factors are constant?
A.
Decreases rate
B.
Increases rate
C.
No effect
D.
Stops photosynthesis
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Solution
Increased light intensity generally increases the rate of photosynthesis, up to a certain point.
Correct Answer:
B
— Increases rate
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Q. What is the main energy carrier produced during the light reactions?
A.
NADPH
B.
ATP
C.
FADH2
D.
Glucose
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Solution
ATP is the main energy carrier produced during the light reactions of photosynthesis.
Correct Answer:
B
— ATP
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Q. What is the main function of the enzyme RuBisCO in photosynthesis?
A.
Fixing carbon dioxide
B.
Producing ATP
C.
Splitting water
D.
Generating NADPH
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Solution
RuBisCO is responsible for fixing carbon dioxide in the Calvin cycle.
Correct Answer:
A
— Fixing carbon dioxide
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Q. What is the main product of the light-dependent reactions of photosynthesis?
A.
Glucose
B.
Oxygen
C.
NADPH
D.
ATP
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Solution
Oxygen is released as a byproduct of the light-dependent reactions.
Correct Answer:
B
— Oxygen
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Q. What is the primary function of the Calvin cycle?
A.
Convert light energy to chemical energy
B.
Fix carbon dioxide into organic molecules
C.
Produce oxygen
D.
Generate ATP
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Solution
The primary function of the Calvin cycle is to fix carbon dioxide into organic molecules.
Correct Answer:
B
— Fix carbon dioxide into organic molecules
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Q. What is the role of water in the light-dependent reactions?
A.
Source of carbon
B.
Electron donor
C.
Energy storage
D.
Oxygen production
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Solution
Water acts as an electron donor in the light-dependent reactions, leading to the production of oxygen.
Correct Answer:
B
— Electron donor
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Q. What is the significance of the electron transport chain in photosynthesis?
A.
Produces glucose
B.
Generates ATP and NADPH
C.
Fixes carbon dioxide
D.
Releases oxygen
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Solution
The electron transport chain generates ATP and NADPH, which are essential for the Calvin cycle.
Correct Answer:
B
— Generates ATP and NADPH
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Q. What is the significance of the proton gradient created during the light-dependent reactions?
A.
Drives ATP synthesis
B.
Fixes carbon
C.
Produces glucose
D.
Generates oxygen
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Solution
The proton gradient drives ATP synthesis through ATP synthase.
Correct Answer:
A
— Drives ATP synthesis
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Q. Which molecule is produced during the Calvin cycle in the dark reactions?
A.
NADPH
B.
ATP
C.
Glucose
D.
Oxygen
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Solution
Glucose is produced during the Calvin cycle, which is part of the dark reactions.
Correct Answer:
C
— Glucose
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