NEET UG · Biology · Photosynthesis in Higher Plants

Calvin and Hatch-Slack Cycles: NEET previous year questions

14 questions in ten years of NEET, in 8 of 10 papers. Pattern: Every year. Here is how it is asked and which ideas come back.

Asked in 10 years: 14; about 1.3 per paper
Years asked: 8/10; last asked 2026
Chance of a question next paper: 84%; historical rate, how we compute it
Weighted estimate: 1.7; model; history: 1.3 a paper on average, typically 0–3

Key findings

01
Asked in 8 of 10 papers, 14 questions in all: #39 of 204 topics by ten-year total. It comes back every 1.3 years on average.
02
100% of its questions since 2018 tested an idea never asked before; none repeated an idea from the year before.
03
The most repeated idea is C3 Reduction and Regen, asked 2 times (2024), usually as “select requirements of a photosynthetic stage”.
04
NEET has asked 13 of the 88 ideas in this topic; 73 have never been asked, directly or indirectly.
05
Mostly asked as one-line MCQ (64%); 43% easy, 0% hard, and up from 0.9 to 2.2 questions a paper since 2024.

Questions per year

Up to 2023: 0.9; per paper
Since 2024: 2.2; +1.3
Usual gap: 1.3 yrs; between papers asking it
Swing: ±1.0; questions, year to year

Recent framings

identify product of a reaction step
numerical: Calvin cycle turns for glucose
count correct statements on photorespiration

Revise first

C3 Reduction and Regen (2024); Calvin Cycle Turns per Glucose (2026); Phosphoglycolate Formation (2026)

How it is asked

Difficulty, format and skill

Across all 14 questions on Calvin and Hatch-Slack Cycles since 2017.

Difficulty

QUESTIONS

Easy6 · 43%
Medium8 · 57%
Hard0 · 0%

Format

One-line MCQ · 9 Q64%
Other · 2 Q14%
Two statements · 2 Q14%
Numerical · 1 Q7%

Skill tested

Concept · 7 Q50%
Recall · 5 Q36%
Calculation · 1 Q7%
Application · 1 Q7%

Repeats

New idea, or one asked before?

Each column is a paper. Blue questions tested an idea NEET had not asked before; navy ones went back to an idea from an earlier paper. 2017 is the first paper, so everything in it counts as new.

’17’18’19’20’21’22’23’24’25’26

Idea asked for the first time
Idea asked in an earlier paper

Coverage of the topic

NEET has asked 13 of the 88 ideas in this topic. 73 have never been asked yet.

1373

Asked directly13 · 15%
Touched inside another question2 · 2%
Never asked73 · 83%

Ideas come from Lumi’s syllabus map of NCERT. A never-asked idea is not a safe skip: most new questions come from exactly these.

Drill down

Idea, year, question

Every idea NEET tested in this topic, with its ten papers. Open one to read the questions.

ideaAskedShareYears’17’18’19’20’21’22’23’24’25’26

2 · 14%14%1/102
- 2024 · Q107
  Which of the following are required for the dark reaction of photosynthesis? A. Light B. Chlorophyll C. CO $_2$ D. ATP E. NADPH Choose the…
  easyOtherNew idea
- 2024 · Q112
  How many molecules of ATP and NADPH are required for every molecule of CO $_2$ fixed in the Calvin cycle?
  easyOne-line MCQNew idea
1 · 7%7%1/10
1 · 7%7%1/10
1 · 7%7%1/10
1 · 7%7%1/10
1 · 7%7%1/10
1 · 7%7%1/10
1 · 7%7%1/10
1 · 7%7%1/10
1 · 7%7%1/10
1 · 7%7%1/10
1 · 7%7%1/10
1 · 7%7%1/10

Squares are the ten papers, 2017 to 2026; darker means more questions. Share is of the level above.

Ideas

Every idea inside this topic

13 different ideas were tested; 1 came more than once. RuBisCO Carboxylation is the foundation for 52 other ideas in the syllabus.

C3 Reduction and Regen2×
select requirements of a photosynthetic stage
Other · 6% next · foundation for 10
Calvin Cycle Turns per Glucose1×
numerical
Numerical · 6% next · foundation for 1
Phosphoglycolate Formation1×
identify product of a reaction step
One-line MCQ · 6% next · foundation for 1
Wasteful Nature of Photorespiration1×
count correct statements on photorespiration
Other · 6% next · foundation for 2
RuBisCO Carboxylation1×
true statement selection on photosynthesis enzyme
One-line MCQ · 6% next · foundation for 52
Photorespiration (C2)1×
statement i/ii on photosynthesis
Two statements · 6% next · foundation for 28
Energy Cost for 1 Glucose in C31×
numerical
One-line MCQ · 4% next · foundation for 2
Kranz Anatomy1×
role of a specialised structure
One-line MCQ · 4% next · foundation for 45
PEP Carboxylase Role1×
statement i/ii on c4 photosynthesis
Two statements · 4% next · foundation for 32
First Stable Product of C4 Cycle1×
identify first stable product of fixation
One-line MCQ · 4% next · foundation for 7
First Products of Photorespiration1×
identify products of enzyme activity
One-line MCQ · 4% next
Light Saturation Points C3 vs C41×
incorrect statement selection on photosynthesis
One-line MCQ · 4% next
Primary CO2 Acceptors Comparison1×
identify example of a type
One-line MCQ · 4% next · foundation for 1

Idea	Times	Format	Chance next	Foundation for
C3 Reduction and Regenselect requirements of a photosynthetic stage	2	OtherConcept	6%	10 ideas
Calvin Cycle Turns per Glucosenumerical	1	NumericalCalculation	6%	1 ideas
Phosphoglycolate Formationidentify product of a reaction step	1	One-line MCQRecall	6%	1 ideas
Wasteful Nature of Photorespirationcount correct statements on photorespiration	1	OtherConcept	6%	2 ideas
RuBisCO Carboxylationtrue statement selection on photosynthesis enzyme	1	One-line MCQConcept	6%	52 ideas
Photorespiration (C2)statement i/ii on photosynthesis	1	Two statementsConcept	6%	28 ideas
Energy Cost for 1 Glucose in C3numerical	1	One-line MCQRecall	4%	2 ideas
Kranz Anatomyrole of a specialised structure	1	One-line MCQConcept	4%	45 ideas
PEP Carboxylase Rolestatement i/ii on c4 photosynthesis	1	Two statementsConcept	4%	32 ideas
First Stable Product of C4 Cycleidentify first stable product of fixation	1	One-line MCQApplication	4%	7 ideas
First Products of Photorespirationidentify products of enzyme activity	1	One-line MCQRecall	4%	–
Light Saturation Points C3 vs C4incorrect statement selection on photosynthesis	1	One-line MCQConcept	4%	–
Primary CO2 Acceptors Comparisonidentify example of a type	1	One-line MCQRecall	4%	1 ideas

Chance next is the historical rate at which an idea with this record came back in the following paper. It is low for every idea, which is why learning the topic beats memorising past questions. All repeated ideas

Every question

Calvin and Hatch-Slack Cycles questions, year by year

The opening words of each question as it appeared in the official paper, with the idea it tested.

NEET 20263 questions

Q100
Photorespiration reaction catalyzed by RuBisCo is shown below : $\mathrm{RuBP+O_2\to}$ 3-Phosphoglycerate + X Identify "X" from the given…
Idea: Phosphoglycolate Formation
New ideaMediumOne-line MCQ
Q116
How many turns of Calvin cycle are required for the formation of three molecules of glucose?
Idea: Calvin Cycle Turns per Glucose
New ideaEasyNumerical
Q122
Which of the following statements regarding photorespiration are correct? (a) Do not occur in C3 plants (b) CO₂ is consumed and O₂ is…
Idea: Wasteful Nature of Photorespiration
New ideaMediumOther

NEET 20251 question

Q171
Which of the following statements about RuBisCO is true?
Idea: RuBisCO Carboxylation
New ideaEasyOne-line MCQ

NEET 20243 questions

Q107
Which of the following are required for the dark reaction of photosynthesis? A. Light B. Chlorophyll C. CO $_2$ D. ATP E. NADPH Choose the…
Idea: C3 Reduction and Regen
New ideaEasyOther
Q112
How many molecules of ATP and NADPH are required for every molecule of CO $_2$ fixed in the Calvin cycle?
Idea: C3 Reduction and Regen
New ideaEasyOne-line MCQ
Q146
Given below are two statements: Statement I : In C $_3$ plants, some O $_2$ binds to RuBisCO, hence CO $_2$ fixation is decreased. Statement…
Idea: Photorespiration (C2)
New ideaMediumTwo statements

NEET 20231 question

Q112
How many ATP and NADPH $_2$ are required for the synthesis of one molecule of Glucose during Calvin cycle?
Idea: Energy Cost for 1 Glucose in C3
New ideaMediumOne-line MCQ

NEET 20222 questions

Q121
Given below are two statements : Statement I : The primary $\mathrm{CO_2}$ acceptor in $\mathrm{C_4}$ plants is phosphoenolpyruvate and is…
Idea: PEP Carboxylase Role
New ideaMediumTwo statements
Q137
What is the role of large bundle shealth cells found around the vascular bundles in $\mathrm{C_4}$ plants ?
Idea: Kranz Anatomy
New ideaMediumOne-line MCQ

NEET 20211 question

Q132
The first stable product of $\mathrm{CO_2}$ fixation in sorghum is :
Idea: First Stable Product of C4 Cycle
New ideaEasyOne-line MCQ

NEET 20201 question

Q42
The oxygenation activity of RuBisCo enzyme in photorespiration leads to the formation of :
Idea: First Products of Photorespiration
New ideaMediumOne-line MCQ

NEET 20172 questions

Q142
With reference to factors affecting the rate of photosynthesis, which of the following statements is not correct ?
Idea: Light Saturation Points C3 vs C4
MediumOne-line MCQ
Q164
Phosphoenol pyruvate (PEP) is the primary $\mathrm{CO_2}$ acceptor in
Idea: Primary CO2 Acceptors Comparison
EasyOne-line MCQ

Questions from the official NEET UG papers published by NTA (CBSE before 2019). Topic and idea tags, counts and notes are Lumi’s.