NEET (UG) · Botany, Class 11
Photosynthesis in Higher Plants: NEET PYQ, 2018–2026
Photosynthesis in Higher Plants (Botany, Class 11) has been asked 19 times in the 7 NEET papers from 2018, 2020, 2021, 2023, 2024, 2025 and 2026: about 2.7 questions a paper, 6% of all Botany questions. It is the 10th most-asked of 17 Botany chapters. NEET 2026 had 5 from it. Last checked 28 October 2026.
Questions per paper
Year by year.
| Year | Questions |
|---|---|
| 2018 | 2 |
| 2020 | 2 |
| 2021 | 2 |
| 2023 | 3 |
| 2024 | 3 |
| 2025 | 2 |
| 2026 | 5 |
From 2021 to 2024 each paper had 200 questions (a Section B with a choice); the others had 180.
Inside the chapter
Topics asked most.
- Light reaction9
- Calvin cycle5
- Photorespiration4
- C4 pathway1
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10 Photosynthesis in Higher Plants questions to practise.
Our own questions, written in the NEET pattern and checked, each with an explanation. Pick an option to see the answer.
Q1 · Botany · Photosynthesis in Higher Plants
How many carbon atoms does ribulose bisphosphate (RuBP), the CO₂ acceptor of the Calvin cycle in C₃ plants, contain?
Answer: (C)
RuBP (ribulose 1,5-bisphosphate) is a pentose (five carbons) with phosphates at C1 and C5. Carboxylation by Rubisco adds CO₂ (one carbon) to give a transient six-carbon compound, which splits into two molecules of 3-PGA. So the acceptor itself has 5 carbons, while the 6-carbon compound is only an unstable intermediate.
Q2 · Botany · Photosynthesis in Higher Plants
In an NADP-malic enzyme C4 plant such as maize, how many ATP molecules are consumed in total to fix one molecule of CO2 into carbohydrate, counting both the C4 cycle and the Calvin cycle?
Answer: (C)
The Calvin cycle requires 3 ATP and 2 NADPH per CO2 fixed. In C4 plants, the mesophyll cell must regenerate PEP from pyruvate, which costs 2 ATP (ATP is converted to AMP plus pyruvate phosphate dikinase activity, so 2 high-energy bonds are used). The total ATP cost per CO2 fixed is therefore 3 + 2 = 5. Students often remember the C3 value of 3 and forget the extra cost of the C4 cycle, or they double-count the C4 regeneration step.
Q3 · Botany · Photosynthesis in Higher Plants
In Hill's experiment, isolated chloroplasts are illuminated in a suspension containing an artificial electron acceptor (such as ferricyanide) but no CO₂. Which result best supports the conclusion that the light reaction can proceed independently of CO₂ fixation?
Answer: (A)
Principle: in the light reaction, PSII splits water and releases O₂, and electrons flow to an acceptor. Hill's experiment used isolated chloroplasts with ferricyanide as an artificial acceptor. O₂ was evolved in light even though no CO₂ was supplied. This shows that the light-dependent water splitting and electron transport are separate from the carbon fixation steps of the Calvin cycle. Students who pick the CO₂-related options are mixing up the light reaction with the dark reactions or with photorespiration.
Q4 · Botany · Photosynthesis in Higher Plants
Why are the C4 acid carbon compounds in C4 plants called 'C4'?
Answer: (A)
In C3 plants the first stable product is 3-phosphoglyceric acid, with three carbons. In C4 plants CO2 first combines with PEP to form oxaloacetic acid, which has four carbons. The pathway is called C4 because of this 4-carbon first product.
Q5 · Botany · Photosynthesis in Higher Plants
How many molecules of ATP does the Calvin cycle consume in fixing enough CO₂ to make one molecule of glucose?
Answer: (D)
Each CO₂ fixed needs 3 ATP (2 in reduction and 1 in the regeneration of RuBP) and 2 NADPH. One glucose needs 6 CO₂, so 6 turns of the cycle: 6 × 3 = 18 ATP, along with 12 NADPH.
Q6 · Botany · Photosynthesis in Higher Plants
In C3 photorespiration, two molecules of glycine formed in the peroxisome are converted to serine in the mitochondrion, releasing CO₂ and NH₃. Where is this NH₃ primarily reassimilated, and by which enzyme pair?
Answer: (A)
Principle: photorespiration releases NH₃ in the mitochondrion when serine is formed from glycine. Free ammonia is toxic and must be recovered. Application: the NH₃ diffuses to the chloroplast, where GS (glutamine synthetase) combines it with glutamate to form glutamine, and GOGAT (glutamate synthase) regenerates glutamate from glutamine and 2-oxoglutarate. This recycling consumes energy, which is part of the cost of photorespiration. Reference: NCERT Class 11, Chapter 13 Photosynthesis in Higher Plants, photorespiration; nitrogen assimilation is covered in Chapter 13 Mineral Nutrition.
Q7 · Botany · Photosynthesis in Higher Plants
Which enzyme can act on RuBP both as a carboxylase, fixing CO2, and as an oxygenase, adding O2, the reaction that starts photorespiration?
Answer: (A)
Photorespiration starts when RuBisCO binds O2 instead of CO2 and oxygenates RuBP. Since RuBisCO is the enzyme that fixes CO2 in the Calvin cycle, its dual carboxylase and oxygenase activity is the origin of the process. Other enzymes in the question either work in a different pathway or in a different organelle.
Q8 · Botany · Photosynthesis in Higher Plants
Compared with C3 plants grown under the same conditions, how do C4 plants compare in water use efficiency, defined as grams of dry matter produced per kilogram of water transpired?
Answer: (B)
Principle: water use efficiency is the carbon gained per unit water lost. Photorespiration in C3 plants forces stomata to stay open for CO2 without gaining much carbon. C4 plants fix CO2 more efficiently at lower internal CO2, so for the same carbon gain they transpire less water. That is why C4 crops are common in hot, dry regions.
Q9 · Botany · Photosynthesis in Higher Plants
In the Hatch and Slack pathway, a 3-carbon molecule is left when the C₄ acid releases its CO₂. Where does this molecule go, and what does it form to complete the cycle?
Answer: (A)
In the bundle sheath cells the C₄ acid is broken down to release CO₂ and a 3-carbon molecule. The CO₂ enters the Calvin cycle there, while the 3-carbon molecule is transported back to the mesophyll, where it is converted to PEP again. This regenerates the primary CO₂ acceptor and makes the Hatch and Slack pathway a cyclic process.
Q10 · Botany · Photosynthesis in Higher Plants
Why do C4 plants show very little photorespiration compared with C3 plants?
Answer: (A)
The key principle is that photorespiration depends on the ratio of O2 to CO2 at the RuBisCO active site. C4 plants pump CO2 into the bundle sheath, where the Calvin cycle runs, so the local CO2 level is high and oxygenation is suppressed. The other options misstate the enzymes, the stomatal role, or the timing of the process.
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All 19 real NEET questions from Photosynthesis in Higher Plants.
The questions from the actual papers, with the official answer and an explanation for each — chapter by chapter, or as full timed papers.
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About Photosynthesis in Higher Plants in NEET.
How many questions come from Photosynthesis in Higher Plants in NEET?
Photosynthesis in Higher Plants (Botany, Class 11) has been asked 19 times in the 7 NEET papers from 2018, 2020, 2021, 2023, 2024, 2025 and 2026: about 2.7 questions a paper, 6% of all Botany questions. It is the 10th most-asked of 17 Botany chapters. NEET 2026 had 5 from it.
Which topics of Photosynthesis in Higher Plants are asked most in NEET?
Light reaction (9), Calvin cycle (5), Photorespiration (4), C4 pathway (1), counted over the papers from 2018–2026.
Is Photosynthesis in Higher Plants important for NEET 2027?
It is in the syllabus in force, so it can be asked. By past papers it ranks 10 of 17 in Botany; use that to decide how much time it gets, not whether to study it.
Where can I solve Photosynthesis in Higher Plants NEET previous year questions?
On Nikaalle, free: sign up and practise every past NEET question from Photosynthesis in Higher Plants with an explanation for each, or sit the full papers timed. The ten questions on this page are our own, written in the same pattern.
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