The five-step mechanism of ribulose bisphosphate carboxylase (rubisco) A) is an overall thermodynamically unstable reaction. B) involves C₁, C₃, C₄, C₅, and C₆ molecules in the enzyme mechanism intermediates. C) adds a CO₂ molecule to a C₅ ribulose sugar, yielding an unstable C₆ molecule that cleaves into two C₃ molecules. D) involves the incorporation of 3 CO₂ molecules to yield one 3-phosphoglycerate molecule.

Question

Quizplus · Accepted Answer

The five-step mechanism of rubisco involves the addition of a CO2 molecule to a ribulose bisphosphate (RuBP) molecule to form an unstable 6-carbon intermediate, which is then cleaved into two molecules of 3-phosphoglycerate. This process involves the intermediates C₁, C₃, C₄, C₅, and C₆, but not CO₂. Choice C correctly describes this process. The reaction is overall thermodynamically favorable, so choice A is incorrect. Choice B includes incorrect molecule identifiers. Choice D states an incorrect stoichiometry of the reaction.

The Five-Step Mechanism of Ribulose Bisphosphate Carboxylase (Rubisco)