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Question
Why is the RuBisCo enzyme more appropriately called RUBP Carboxylase-Oxygenase and what important role does it play in photosynthesis?
Solution
RuBisCO enzyme has an affinity towards carbon dioxide as well as towards oxygen. But this binding is competitive. It has a considerable affinity towards carbon dioxide than towards oxygenation. It is the relative concentration of CO2 and O2 which affects the binding of RuBisCO to a particular molecule. Since it acts like carboxylase as well as like oxygenase; it is more appropriately called RUBP Carboxylase–Oxygenase.
Importance of RuBisCO: In C3 plants, RuBisCO bonds with CO2 to generate 3PGA. In C3 plants, some of the RuBisCO binds with O2 to produce phosphoglycerate and phosphoglycolate through a process called photorespiration. Photorespiration reduces carbon fixation in C3 plants.
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RELATED QUESTIONS
Even though a very few cells in a C4 plant carry out the biosynthetic – Calvin pathway, yet they are highly productive. Can you discuss why?
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\[\ce{3CO2 + 9ATP + 6NADPH + Water -> glyceraldehyde 3 – phosphate + 9 ADP + 6 NADP+ + 8 Pi}\]
Analyze the above reaction and answer the following questions:
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Six turns of calvin cycle are required to generate one mole of glucose. Explain.
