What is the function of ribulose bisphosphate (RuBP) during photosynthesis?

A) It produces the CO₂ needed for photosynthesis.
B) It combines with CO₂ to produce a 6-carbon compound.
C) It combines with ATP to form G3P.
D) It splits water to release oxygen.
E) It splits carbon dioxide to release oxygen.

Ribulose bisphosphate (RuBP) is a 5-carbon sugar that plays a crucial role in the process of carbon fixation, which is the first step in photosynthesis. RuBP combines with carbon dioxide (CO2) to produce two molecules of a 3-carbon compound called 3-phosphoglycerate (3PG). This reaction is catalyzed by the enzyme RuBisCO (ribulose bisphosphate carboxylase/oxygenase), and it is the starting point for the Calvin cycle, which ultimately leads to the production of glucose.