Photosynthesis is the process whereby plants and algae use light energy to fix carbon dioxide as sugars. Although it is often represented by one highly simplified equation – 6H2O + 6CO2 –> C6H12O6 + 6O2– it is in reality a more complex series of spatially and temporally separated reactions.
Photosynthesis largely comprises two linked processes:
- the light-dependent reactions – in which light energy excites electrons split from water, driving an electron transport chain and proton-pumping which ultimately result in the production of ATP (adenosine triphosphate, the universal biological energy currency) and NADPH (reduced nicotinamide adenine dinucleotide phosphate, a reducing agent)
- the light-independent reactions – the Calvin Cycle, in which CO2 is fixed into organic molecules by the enzyme RuBisCO.