Which speeds up the reaction between carbon dioxide and RuBP to restart the Calvin Cycle?

Rubisco is the enzyme that catalyzes the reaction between carbon dioxide and RuBP at the start of the Calvin cycle. Enzymes speed up reactions, so rubisco is the correct choice. 3-phosphoglycerate and glyceraldehyde 3-phosphate are products or intermediates in the cycle, and light energy does not directly catalyze this reaction.

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