Calvin Cycle

The Calvin cycle is also known as the light independent reactions, as they can occur in the dark. It occurs inside the stroma of the chloroplasts. There are three stages: carbon dioxide fixation, reduction of carbon dioxide, and regeneration of ribulose biphosphate.

Carbon dioxide is initially accepted by ribulose biphosphate to become a 6 carbon unstable intermediate, which breaks down to form two molecules of 3 phosphoglycerate. This reaction is catalysed by RuBP carboxylase, or Rubisco. 3-phosphoglycerate is later phosphorylated by a molecule of ATP to form 1,3-biphosphoglycerate and ADP. 1,3-biphosphoglycerate is later reduced by NADPH to form phosphoglyceraldehyde (GALP) and NADP. 1/6 of all GALP formed is channelled to form sugars and other useful substances for the plant. The remaining 5/6 of GALP undergoes a series of chemical reactions and is phosphorylated by ATP again to regenerate RuBP.