NEET 2026 (Phase 1) · BiologyPrevious Year Question
The enzyme required for carboxylation in the Calvin cycle is
Answer: (C) RuBP carboxylase - oxygenase. The carboxylation step of the Calvin cycle is catalysed by RuBP carboxylase, more correctly called RuBP carboxylase-oxygenase (RuBisCO), which fixes CO2 onto RuBP to form two molecules of 3-PGA.
- A.Hexokinase
- B.PEP carboxylase
- C.RuBP carboxylase - oxygenase✓
- D.Carboxypeptidase
Correct Answer
(C) RuBP carboxylase - oxygenase
Solution & Explanation
The carboxylation step of the Calvin cycle is catalysed by RuBP carboxylase, more correctly called RuBP carboxylase-oxygenase (RuBisCO), which fixes CO2 onto RuBP to form two molecules of 3-PGA. PEP carboxylase is the C4 mesophyll carboxylation enzyme, so it is a distractor. Hence the answer is RuBP carboxylase-oxygenase. NCERT: Class 11 Ch 11, p.143 [143:041]: "or RuBisCO."
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