THE MECHANISM OF PIIOTC SYNTHESIS 

 Eugene Rabinowitch 



I. 



Photosynthesis is a tripartite process, as indicated 

 schematically in figure 1 — one reaction set dealing with the 

 conversion of CO^ to organic matter, one with the liberation 

 of oxygen from water, and one with the conversion of light 

 into chemical energy. 



CO2 



X (-0.4V) 



T 



{CH20) 



Chl 



HcO 



-0; 



ZH(+0.8V) 



Fig. 1 



The first two sets are "dark," enzymatic processes, occur- 

 ring at an approximately constant level of energy, the 

 third an energy-accumulating photochemical process. This 

 latter must be an oxidation-rcduction --either hydrogen atom 

 transfer, or electron transfer, or a combination of both. 

 This transfer goes from a donor, ZH (an intermediate in the 



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