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NEET 2024, Biology Q41: Dark Reactions and Photorespiration

NEET2024Biology
Q.

Given below are two statements:

Statement I: In C plants, some O binds to RuBisCO, hence CO fixation is decreased.
Statement II: In C plants, mesophyll cells show very little photorespiration while bundle sheath cells do not show photorespiration.

In the light of the above statements, choose the correct answer from the options given below:

  1. A

    Statement I is true but Statement II is false

  2. B

    Statement I is false but Statement II is true

  3. C

    Both Statement I and Statement II are true

  4. D

    Both Statement I and Statement II are false

Solution

In C plants RuBisCO can bind O instead of CO (it has dual carboxylase / oxygenase activity), reducing CO fixation — Statement I is correct. In C plants, primary CO fixation occurs in mesophyll cells by PEP carboxylase (which has no oxygenase activity), and the Calvin cycle (with RuBisCO) is confined to bundle sheath cells where CO is concentrated; so photorespiration is essentially absent in both cell types of C plants, not just bundle sheath. Statement II is therefore incorrect as worded.

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