Important Questions Class 11 Biology Chapter 11 Photosynthesis in Higher Plants 2026–27

Photosynthesis in Higher Plants explains how green plants convert light energy into chemical energy through chloroplast-based reactions.
For CBSE Class 11 Biology, Important Questions Class 11 Biology Chapter 11 help revise pigments, light reactions, Calvin cycle, C4 pathway and photorespiration.

Photosynthesis in Higher Plants is Chapter 11 in the updated NCERT Class 11 Biology textbook for 2026–27. It explains how green plants use light energy to synthesise carbohydrates from carbon dioxide and water. The chapter covers chloroplasts, photosynthetic pigments, light reaction, ATP and NADPH formation, Calvin cycle, C4 pathway, photorespiration and factors affecting photosynthesis.

Use these Important Questions Class 11 Biology Chapter 11 to revise definitions, processes, diagrams, comparisons and long-answer concepts. Start with photosynthesis and pigments, then revise light reaction, photophosphorylation, chemiosmosis, Calvin cycle, C3 and C4 pathways, photorespiration and limiting factors.

Key Takeaways

• Photosynthesis: It is the process by which green plants use light energy to synthesise organic compounds.
• Light reaction: It occurs in thylakoid membranes and produces ATP, NADPH and oxygen.
• Calvin cycle: It occurs in the stroma and uses ATP and NADPH to fix carbon dioxide into sugars.
• C4 plants: They show Kranz anatomy, reduce photorespiration and perform well under high light and temperature.

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Very Short Answer Questions for Important Questions Class 11 Biology Chapter 11

Photosynthesis in Higher Plants begins with basic facts about pigments, chloroplasts, photosystems and carbon fixation. These answers help revise NCERT Class 11 Biology Chapter 11 before process-based questions.

Q1. What is photosynthesis?

Photosynthesis is a physico-chemical process by which green plants use light energy to synthesise organic compounds.

In this process, carbon dioxide and water form carbohydrates. Oxygen is released as a by-product.

Q2. Why is photosynthesis important?

Photosynthesis is important because it is the primary source of food on earth.

It also releases oxygen into the atmosphere. Most living organisms depend directly or indirectly on photosynthesis for energy.

Q3. Which organelle is the site of photosynthesis?

Chloroplast is the site of photosynthesis.

In leaves, mesophyll cells contain many chloroplasts. These chloroplasts help in light absorption and carbon dioxide fixation.

Q4. Name the chief pigment associated with photosynthesis.

Chlorophyll a is the chief pigment associated with photosynthesis.

It absorbs light mainly in the blue and red regions. It directly participates in the reaction centre.

Q5. Name two accessory pigments involved in photosynthesis.

Chlorophyll b and carotenoids are accessory pigments involved in photosynthesis.

Xanthophylls are also accessory pigments. They absorb light and transfer energy to chlorophyll a.

Q6. What are the end products of the light reaction?

The end products of the light reaction are ATP, NADPH and oxygen.

ATP and NADPH are used in carbon fixation reactions. Oxygen diffuses out of the chloroplast.

Q7. What is Kranz anatomy?

Kranz anatomy is the special arrangement of large bundle sheath cells around vascular bundles in C4 plants.

These bundle sheath cells have many chloroplasts, thick walls and no intercellular spaces.

Q8. Which enzyme fixes carbon dioxide in the Calvin cycle?

RuBisCO fixes carbon dioxide in the Calvin cycle.

Its full name is ribulose bisphosphate carboxylase-oxygenase. It catalyses the carboxylation of RuBP.

Objective Questions Class 11 Biology Chapter 11

Objective questions from Photosynthesis in Higher Plants test exact NCERT terms, reaction centres and first stable products. They also cover one-word answers, MCQs and true or false facts.

Q9. Choose the correct The reaction centre of Photosystem I is called ______.

1. a) P680
   b) P700
   c) RuBP
   d) OAA
2. b) P700.

Photosystem I has a reaction centre that absorbs light at 700 nm.

Q10. Choose the correct The reaction centre of Photosystem II is called ______.

1. a) P680
   b) P700
   c) PGA
   d) PEP
2. a) P680.

Photosystem II has a reaction centre that absorbs red light at 680 nm.

Q11. Choose the correct The primary acceptor of carbon dioxide in the Calvin cycle is ______.

1. a) PEP
   b) RuBP
   c) OAA
   d) NADPH
2. b) RuBP.

Ribulose bisphosphate is the five-carbon primary carbon dioxide acceptor in the Calvin cycle.

Q12. Choose the correct The first stable product of the C4 pathway is ______.

1. a) PGA
   b) RuBP
   c) OAA
   d) ATP
2. c) OAA.

Oxaloacetic acid is the first stable product of carbon dioxide fixation in C4 plants.

Q13. Fill in the blank: Cyclic photophosphorylation produces only ______.

ATP.

In cyclic photophosphorylation, the excited electron returns to Photosystem I. NADPH and oxygen are not produced.

Q14. True or False: Oxygen released during photosynthesis comes from carbon dioxide.

False.

Oxygen released during photosynthesis comes from water. Van Niel inferred this, and later radioisotopic studies supported it.

Q15. Match the following: Photosystem I, Photosystem II, P700 and P680.

Photosystem I matches with P700, and Photosystem II matches with P680.

P700 absorbs light at 700 nm. P680 absorbs red light at 680 nm.

Q16. True or False: C4 plants show negligible photorespiration.

True.

C4 plants increase carbon dioxide concentration near RuBisCO. This reduces oxygenase activity and limits photorespiration.

Short Answer Questions Class 11 Biology Chapter 11

Short Answer Questions from Photosynthesis in Higher Plants often test experiments, pigments and reaction steps. Use terms such as chloroplast, chlorophyll a, RuBisCO, photophosphorylation and photorespiration correctly.

Q17. What did Priestley’s experiment show about plants?

Priestley’s experiment showed that plants restore air damaged by burning candles or breathing animals.

He placed a mint plant with a candle or mouse in a bell jar. The plant helped the candle burn and the mouse survive longer.

This experiment showed that plants play an important role in maintaining air quality.

Q18. What did Ingenhousz prove through his experiment?

Ingenhousz proved that sunlight and green parts of plants are necessary for oxygen release.

He showed that bubbles appeared around green parts of aquatic plants in bright sunlight. These bubbles were later identified as oxygen.

His work showed that light is essential for photosynthesis.

Q19. What was Engelmann’s contribution to photosynthesis?

Engelmann described the first action spectrum of photosynthesis.

He split light into spectral components and illuminated a green alga placed in a suspension of aerobic bacteria.

The bacteria gathered mainly in blue and red light regions. This showed where maximum oxygen evolution occurred.

Q20. What did van Niel infer about oxygen evolution in photosynthesis?

Van Niel inferred that oxygen evolved in photosynthesis comes from water, not carbon dioxide.

He studied purple and green sulphur bacteria. He showed that photosynthesis uses hydrogen from a suitable donor.

In green plants, water acts as the hydrogen donor. Its splitting releases oxygen.

Q21. Where do light reaction and carbon fixation reactions occur in the chloroplast?

Light reaction occurs in the thylakoid membranes, while carbon fixation reactions occur in the stroma.

The thylakoid membranes trap light energy and form ATP and NADPH.

The stroma uses ATP and NADPH for carbon dioxide fixation and sugar synthesis.

Q22. Why is chlorophyll a called the chief pigment of photosynthesis?

Chlorophyll a is called the chief pigment because it directly participates in the reaction centre.

It absorbs light strongly in the blue and red regions.

Other pigments absorb light and transfer energy to chlorophyll a. This makes chlorophyll a central to photosynthesis.

Q23. What is the difference between absorption spectrum and action spectrum?

Absorption spectrum shows the wavelengths of light absorbed by a pigment.

Action spectrum shows the wavelengths at which photosynthesis is most effective.

In photosynthesis, the action spectrum roughly resembles the absorption spectrum of chlorophyll a and b. Maximum photosynthesis occurs mainly in blue and red regions.

Q24. What is photolysis of water?

Photolysis of water is the splitting of water during the light reaction.

It is associated with Photosystem II and produces protons, electrons and oxygen.

The electrons replace those lost by Photosystem II. Oxygen is released as a product of photosynthesis.

Long Answer Questions Class 11 Biology Chapter 11

Long Answer Questions from Photosynthesis in Higher Plants need definitions, steps and correct sequence. Write light reaction, electron flow, Calvin cycle, C4 pathway and limiting factors with NCERT-based terms.

Q25. Explain cyclic and non-cyclic photophosphorylation.

Photophosphorylation is the synthesis of ATP from ADP and inorganic phosphate in the presence of light.

It is of two types: cyclic and non-cyclic.

In cyclic photophosphorylation, only Photosystem I functions. The excited electron returns to Photosystem I through the electron transport chain. Only ATP is formed.

In non-cyclic photophosphorylation, both Photosystem II and Photosystem I work in series. Electrons move from water to Photosystem II, then to Photosystem I and finally to NADP+. ATP, NADPH and oxygen are produced.

Q26. Explain the chemiosmotic hypothesis of ATP synthesis in chloroplasts.

The chemiosmotic hypothesis explains ATP synthesis through a proton gradient across the thylakoid membrane.

During light reaction, protons accumulate inside the thylakoid lumen.

This happens because water splits on the inner side of the membrane. Electron transport also moves protons into the lumen. NADP reductase removes protons from the stroma during NADPH formation.

The proton gradient breaks down when protons move back to the stroma through ATP synthase. This movement provides energy for ATP synthesis.

Q27. Describe the Calvin cycle and mention the ATP and NADPH requirement for one glucose molecule.

The Calvin cycle is the carbon fixation pathway that forms sugars using ATP and NADPH.

It occurs in the stroma of chloroplasts and operates in all photosynthetic plants.

The first stage is carboxylation. Carbon dioxide combines with RuBP in the presence of RuBisCO to form two molecules of 3-PGA.

The second stage is reduction. ATP and NADPH convert 3-PGA into carbohydrate intermediates.

The third stage is regeneration. RuBP is regenerated so the cycle can continue.

For one glucose molecule, six turns of the Calvin cycle use 18 ATP and 12 NADPH.

Q28. Explain the C4 pathway or Hatch and Slack pathway.

The C4 pathway is a carbon fixation pathway found in plants adapted to dry tropical regions.

In these plants, the first stable product of carbon dioxide fixation is oxaloacetic acid, a four-carbon compound.

The primary carbon dioxide acceptor is phosphoenol pyruvate, or PEP. PEP carboxylase fixes carbon dioxide in mesophyll cells to form OAA.

OAA changes into other C4 acids such as malic acid or aspartic acid. These acids move to bundle sheath cells, where carbon dioxide is released.

The released carbon dioxide enters the Calvin cycle. This arrangement helps C4 plants reduce photorespiration.

Q29. Differentiate between C3 and C4 plants.

C3 plants fix carbon dioxide directly through RuBP, while C4 plants first fix carbon dioxide through PEP.

In C3 plants, the first stable product is 3-PGA. In C4 plants, the first stable product is OAA.

The Calvin cycle occurs in mesophyll cells of C3 plants. In C4 plants, it occurs in bundle sheath cells.

C4 plants show Kranz anatomy and negligible photorespiration. They are more productive under high light and high temperature conditions.

Q30. What is photorespiration and why is it considered wasteful?

Photorespiration is a process in which RuBisCO binds with oxygen instead of carbon dioxide.

In C3 plants, RuBP combines with oxygen to form one molecule of phosphoglycerate and one molecule of phosphoglycolate.

Photorespiration is considered wasteful because it does not produce sugars, ATP or NADPH. It also releases carbon dioxide and uses ATP.

C4 plants avoid photorespiration by increasing carbon dioxide concentration near RuBisCO in bundle sheath cells. This helps RuBisCO act mainly as a carboxylase.

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