H2O+ CO2=C6H12O6+O2
The above equation shows the process of photosynthesis but why do we call it a reduction reaction when along with hydrogen, oxygen is also added to glucose?

Photosynthesis is not just a reduction reaction but a redox reaction.
 Redox reactions (short for oxidation-reduction reactions) involve the transfer of electrons. During oxidation, a substance loses its electrons whereas, during reduction, a substance gains electrons.

 Photosynthesis is a process in which plants containing chlorophyll convert the carbon dioxide into sugars in the presence of sunlight by a set of redox reactions. 
Calvin cycle represents a set of reactions that remove electrons from water which are then used to turn carbon dioxide into organic compounds.
Redox reactions during photosynthesis :
It involves two steps - 
The first step is the oxidation in oxygen in the water molecule in the presence of light
2H2O → O2+ 4H+

The second step is the reduction step where hydrogen ions reduce the carbon in carbon dioxide
4H+ + CO2  →  (CH2 O) + H20

The net reaction is 
CO2+ 2H2O → (CH2O) + O2


Updated on: 29-Mar-2023

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