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The relative concentration of which two gases decides whether RuBisCO acts as a carboxylase or an oxygenase?

  • (a) CO2 and water vapour Your answer
  • (b) O2 and CO2 Correct
  • (c) N2 and O2 Your answer
  • (d) O2 and water vapour Your answer
Your answer: Correct answer: (b)
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Explanation

Why (b) is correct

RuBisCO can bind O2 or CO2. Which one it binds depends on the relative concentration of O2 and CO2.

Why the other options are wrong

  • (a) · your answer Water vapour does not compete for RuBisCO.
  • (c) · your answer Nitrogen does not bind RuBisCO.
  • (d) · your answer Water vapour does not bind RuBisCO.
NCERT point: High O2 and low CO2 favour the oxygenase activity.
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