The Dark Reactions (Light Independent)

What you need to know about the dark reactions.


  1. They can occur with or without light.


  1. They occur in the stroma of chloroplasts.


  1. The dark reaction requires ATP and NADPH -- products of the light reaction.


  1. In addition the dark reaction requires CO2, RuBP (a 5-carbon sugar called ribulose bisphosphate), and rubisco (the most plentiful enzyme on earth.


  1. One glucose molecule is formed only after 6 turns of the Calvin cycle.


  1. The 6-carbon molecule first formed by rubisco is unstable and is quickly converted to 2 molecules of PGAL (glyceraldehyde-3-phosphate also known as G3P). PGAL can be returned to the Calvin cycle as RuBP or used in glycolysis and several other anabolic processes to make amino acids or lipids.