 In plants, cyanobacteria and algae, oxygenic photosynthesis splits water, with oxygen produced as a waste product.This process uses the ATP and NADPH produced by the photosynthetic reaction centres, as described above, to convert CO2 into glycerate 3-phosphate, which can then be converted into glucose.This carbon-fixation reaction is carried out by the enzyme RuBisCO as part of the Calvin – Benson cycle.