Question

Rubisco carries on a dual role as carboxylase as well as oxygenase. Explain for 3 marks

Answer 1

RuBisCO or Ribulose-1,5-biphosphate carboxylase/oxygenase is the enzyme that catalyses the first step of Calvin cycle called carboxylation or carbon fixation. During this step, CO₂ combines with a 5-crbon sugar called ribulose-1,5-biphosphate.
RuBisCO, however, also functions as RuBP oxygenase in presence of high concentration of oxygen. This happens during photorespiration where a large amount of carbon dioxide fixed during photosynthesis is lost.