C3 Pathway (Calvin Cycle) — NEET Biology MCQs with Solutions
Free NEET Biology C3 Pathway (Calvin Cycle) MCQs with step-by-step solutions (6 questions). Part of Photosynthesis in Higher Plants. Practise online on Prepizo — no login needed.
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Questions with solutions
Q1 — C3 Pathway (Calvin Cycle) · easy · theory
The primary CO₂ acceptor in the Calvin (C3) cycle is:
A. RuBP (ribulose-1,5-bisphosphate) ✓ Correct
B. PEP
C. OAA
D. Pyruvate
Solution: RuBP (5-C) accepts CO₂; the first stable product is 3-PGA (a 3-carbon acid) — hence "C3".
Q2 — C3 Pathway (Calvin Cycle) · easy · theory
The first stable product of carbon fixation in the C3 pathway is:
A. Glucose
B. Oxaloacetic acid
C. Malic acid
D. 3-phosphoglyceric acid (3-PGA) ✓ Correct
Solution: CO₂ + RuBP → 2 molecules of 3-PGA (3-carbon), catalysed by RuBisCO.
Q3 — C3 Pathway (Calvin Cycle) · medium · theory
The enzyme catalysing CO₂ fixation in the Calvin cycle is:
A. ATP synthase
B. PEP carboxylase
C. NADP reductase
D. RuBisCO (ribulose bisphosphate carboxylase-oxygenase) ✓ Correct
Solution: RuBisCO is the most abundant enzyme; it carboxylates RuBP but can also oxygenate it (photorespiration).
Q4 — C3 Pathway (Calvin Cycle) · medium · theory
To fix ONE molecule of CO₂ in the Calvin cycle, the cell uses:
A. 1 ATP and 1 NADPH
B. 2 ATP and 3 NADPH
C. 3 ATP and 2 NADPH ✓ Correct
D. 18 ATP only
Solution: Per CO₂: 3 ATP + 2 NADPH; six turns (6 CO₂) make one glucose using 18 ATP and 12 NADPH.
Q5 — C3 Pathway (Calvin Cycle) · hard · theory
The three phases of the Calvin cycle are, in order:
A. Regeneration → carboxylation → reduction
B. Carboxylation → reduction → regeneration (of RuBP) ✓ Correct
C. Reduction → regeneration → carboxylation
D. Carboxylation → regeneration → reduction
Solution: Carboxylation (CO₂ + RuBP), reduction (3-PGA → G3P using ATP/NADPH), and regeneration of RuBP.
Q6 — C3 Pathway (Calvin Cycle) · hard · theory
To synthesise one glucose molecule, the Calvin cycle must turn ______ times, fixing ______ CO₂:
A. 6; 6 ✓ Correct
B. 1; 6
C. 12; 12
D. 3; 3
Solution: Six turns fix six CO₂ molecules, consuming 18 ATP and 12 NADPH to produce one hexose.