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HomeNEET UGbiologyPhotosynthesis in Higher Plants › Photorespiration in C3 plants is wasteful because

Photorespiration in C3 plants is wasteful because

Ait uses water without producing sugar but releases pure ATP
Bit produces glucose at twice the normal rate
CRuBisCO fixes O₂ instead of CO₂; no ATP, no sugar, carbon lost as CO₂
Dit requires a separate enzyme rarely synthesised
Answer & Solution
Correct answer: C. RuBisCO fixes O₂ instead of CO₂; no ATP, no sugar, carbon lost as CO₂
Photorespiration starts when RuBisCO's oxygenase activity wins over its carboxylase activity (favoured by high O₂ and low CO₂ inside the leaf in heat). The resulting 2-carbon phosphoglycolate is processed at metabolic cost, and some carbon is released back as CO₂. C4 plants bypass this entirely.
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