Photosynthesis is a two-step process whereby cells harness light energy to synthesise organic molecules

• The light dependent reactions convert light energy into chemical energy (ATP) and splits water to release hydrogen atoms
  

• The light independent reactions use the chemical energy to fuse the hydrogen atoms to a carbon source (CO2), producing organic compounds
  

The two photosynthetic reactions are interdependent – each requires completion of the other in order to occur

• The light independent reaction cannot occur without the products of the light dependent reaction (ATP and NADPH)
  

• The light dependent reaction requires an unloaded coenzyme (NADP) to carry the hydrogen atoms – this coenzyme is unloaded by the light independent reaction
  

  • Hence, a lack of carbon dioxide in the light independent reaction will prevent the production of NADPH by photosystem II in the light dependent stage