The light-independent reactions or darkness reactions of photosynthesis are chemical reactions that convert CO2 and others compounds into glucose. These reactions occur in the stroma, the fluid-filled area of a chloroplast outside of the thylakoid membranes. These reaction takes the product of light-dependent reactions and performs the further chemical process on them. There are three phases to the light-dependent reaction, collectively called the Calvin cycle. The first step of the Calvin cycle is carboxylation in which a CO2 molecule combines with a fire carbon molecule called ribulose, 1.5 biphosphates (RUBP), and produces a six-carbon containing that split into two molecules of a three-carbon compound 3 phosphoglyceric acids (3-PGA). This reaction is catalyzed by the enzyme RUBP carboxylase.