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NEET 2025, Biology Q24: Dark Reactions and Photorespiration

NEET2025Biology
Q.

Which of the following statements about RuBisCO is true?

  1. A

    It catalyzes the carboxylation of RuBP

  2. B

    It is active only in the dark

  3. C

    It has higher affinity for oxygen than carbon dioxide

  4. D

    It is an enzyme involved in the photolysis of water

Solution

RuBisCO (Ribulose-1,5-bisphosphate carboxylase-oxygenase) catalyses the very first carbon-fixing step of the Calvin cycle — the carboxylation of RuBP using CO.

Although RuBisCO also has oxygenase activity, its affinity is greater for CO than O, so option (3) is incorrect. Photolysis of water occurs in PS II, not via RuBisCO.

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