Which enzyme catalyzes the fixation of CO2 to RuBP in the Calvin cycle?

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Multiple Choice

Which enzyme catalyzes the fixation of CO2 to RuBP in the Calvin cycle?

The fixation of CO2 to RuBP in the Calvin cycle is carried out by Rubisco, ribulose-1,5-bisphosphate carboxylase/oxygenase. This enzyme catalyzes the carboxylation step that adds CO2 to RuBP, forming an unstable six-carbon intermediate that quickly splits into two molecules of 3-phosphoglycerate. Rubisco is the most abundant enzyme on Earth and operates in the chloroplast stroma, though it can also catalyze an oxygenation reaction under certain conditions, leading to photorespiration. The other enzymes listed have different roles: NADP+ reductase transfers electrons to produce NADPH for the Calvin cycle; ATP synthase generates ATP using the proton gradient; and pyruvate kinase drives a step in glycolysis.

The fixation of CO2 to RuBP in the Calvin cycle is carried out by Rubisco, ribulose-1,5-bisphosphate carboxylase/oxygenase. This enzyme catalyzes the carboxylation step that adds CO2 to RuBP, forming an unstable six-carbon intermediate that quickly splits into two molecules of 3-phosphoglycerate. Rubisco is the most abundant enzyme on Earth and operates in the chloroplast stroma, though it can also catalyze an oxygenation reaction under certain conditions, leading to photorespiration. The other enzymes listed have different roles: NADP+ reductase transfers electrons to produce NADPH for the Calvin cycle; ATP synthase generates ATP using the proton gradient; and pyruvate kinase drives a step in glycolysis.

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