What does RuBisCO catalyze in the Calvin cycle?

RuBisCO, or ribulose bisphosphate carboxylase/oxygenase, plays a pivotal role in the Calvin cycle by catalyzing the incorporation of carbon dioxide (CO2) into ribulose 1,5-bisphosphate (RuBP). This reaction is the first step in the process of carbon fixation, which is essential for converting inorganic carbon from the atmosphere into organic compounds that plants can use for energy and growth.

When CO2 is added to RuBP, the resulting 6-carbon intermediate quickly splits into two molecules of 3-phosphoglycerate (3-PGA). This transformation is crucial for enabling the subsequent steps of the Calvin cycle, during which 3-PGA will ultimately be converted into glucose and other carbohydrates.

This function of RuBisCO is fundamental to the process of photosynthesis, as it directly influences the ability of plants to capture atmospheric CO2 and convert it into sugar, making it a vital component of the ecosystem and the global carbon cycle.