Question: 171. Which of the following statements about RuBisCO is true?
(1) It is active only in the dark.
(2) It has higher affinity for oxygen than carbon dioxide.
(3) It is an enzyme involved in the photolysis of water.
(4) It catalyzes the carboxylation of RuBP.
Answer: Option (4)
Explanation:
RuBisCO stands for Ribulose-1,5-bisphosphate carboxylase/oxygenase.
It is the key enzyme of the Calvin cycle occurring in the stroma of chloroplasts.
RuBisCO catalyzes the carboxylation of ribulose-1,5-bisphosphate (RuBP) by adding carbon dioxide.
This reaction leads to the formation of two molecules of 3-phosphoglycerate.
RuBisCO is active in the light because the Calvin cycle depends on ATP and NADPH produced during light reactions.
RuBisCO has a higher affinity for carbon dioxide than oxygen under normal conditions.
It is not involved in the photolysis of water, which occurs in the light reactions.
Therefore, the correct statement is that RuBisCO catalyzes the carboxylation of RuBP.