Q. 9
Why is the Rubisco enzyme more appropriately called RUBP Carboxylase-Oxygenase and what important role does it play in photosynthesis?
Answer :
Both carbon dioxide and oxygen have affinity with the enzyme of Rubisco. This is competitive, however. It is more closely related to CO2 than to oxygenation. It is the relative CO2 and O2 concentration that affects Rubisco’s binding to a particular molecule. Since it acts as both carboxylase and oxygenase, RUBP carboxylase–Oxygenase is better referred to.
Rubisco binds CO2 to 3PGA in C3 plants. In C3 plants, Rubisco is binding with O2 in a process known photorespiration to generate phosphoglycerate and phosphoglycerate. Photo vacuum reduces carbon attachment in C3 plants
Rubisco catalyses the production of oxaloacetic acid in C4 plants due to the increase in carbon dioxide levels in the vascular bundle. In this case, photorespiration is avoided and carbon fixation is more efficient.
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