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Biology · PYQ NEET UG 2024
हिन्दीGiven below are two statements: Statement I: In \( \text{C}_3 \) plants, some \( \text{O}_2 \) binds to RuBisCO, hence \( \text{CO}_2 \) fixation is decreased. Statement II: In \( \text{C}_4 \) 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:
Correct answer · Option 1
Statement I is true but Statement II is false
Explanation
Statement I is correct because in \( \text{C}_3 \) plants, RuBisCO has an affinity for both \( \text{CO}_2 \) and \( \text{O}_2 \). Under high \( \text{O}_2 \) or low \( \text{CO}_2 \) conditions, \( \text{O}_2 \) binds to RuBisCO, leading to photorespiration (C2 cycle) which decreases net \( \text{CO}_2 \) fixation. Statement II is incorrect because \( \text{C}_4 \) plants have evolved a mechanism (Kranz anatomy and \( \text{C}_4 \) pathway) that virtually eliminates photorespiration entirely in both mesophyll and bundle sheath cells. Therefore, Statement I is true and Statement II is false.
