1. Carbon Fixation: Carbon dioxide from the atmosphere is incorporated into an existing five-carbon sugar called RuBP (ribulose bisphosphate). This process is catalyzed by the enzyme RuBisCo. The result is a six-carbon molecule that quickly splits into two molecules of 3-PGA (3-phosphoglycerate), a three-carbon compound.
2. Reduction: The 3-PGA molecules are then converted into G3P (glyceraldehyde-3-phosphate), a three-carbon sugar. This conversion requires energy from ATP (produced in the light-dependent reactions) and reducing power from NADPH (also produced in the light-dependent reactions).
3. Regeneration: Most of the G3P molecules are used to regenerate RuBP, so the cycle can continue. This process requires ATP and consumes some of the G3P produced. A small amount of G3P escapes the cycle and is used to synthesize other organic molecules like glucose.
Therefore, the 3 basic events of the light-independent reactions are carbon fixation, reduction, and regeneration.
