Final answer:
RuBisCO catalyzes a reaction between CO₂ and ribulose 1,5-bisphosphate, resulting in the production of 3-phosphoglyceric acid (3-PGA).
Step-by-step explanation:
RuBisCO catalyzes a reaction between CO₂ and ribulose 1,5-bisphosphate (RuBP) in the Calvin Cycle of photosynthesis. This reaction results in the production of two molecules of 3-phosphoglyceric acid (3-PGA). Each 3-PGA molecule contains three carbon atoms and one phosphate group.