PHOTOSYNTHESIS 



system, the full 42 kcal. might be transferred to a suitable proxi- 

 mate acceptor, at least insofar as competition with fluorescence 

 is concerned. 



The conversion of electronic energy to chemical energy may 

 involve either the transfer of electronic energy to some acceptor 

 molecule other than chlorophyll followed by energy conversion, 

 or the transfer of an electron from the chlorophyll aggregate 

 (array) to some other molecule and a corresponding recovery of 

 an electron by the positively charged chlorophyll molecule group 

 from some other source. Either of these types of conversion 

 seems possible at the present time, and we will consider both. 



In order to accept electronic energy from chlorophyll and 

 convert it to chemical energy, a compound, which could be 

 called the quantum converter, should possess several properties. 

 It would have to be closely associated with, or incorporated in, 

 the chlorophyll aggregate, and should possess some state differing 

 from its ground state by about 30 to 40 kcal., in order to accept 

 the energy of a quantum from the chlorophyll. It would convert 

 this energy by some process which occurs in a time that is short 

 compared to the time required for the return of the energy to 

 chlorophyll or its dissipation in a nonuseful way, and in so doing 

 would form new chemical configurations which would store most 

 of the energy received from the chlorophyll. By new chemical 

 configurations, we mean only that some nuclei would have moved 

 sufficiently to prevent the loss of the received energy either by 

 its return to the donor or conversion to heat ; that is, the energy 

 would now be trapped in a new configuration which could not 

 return easily to the former one. 



When the energy had undergone this conversion, the 

 quantum converter, in its new form, would pass the energy on. 

 Since, in this picture, the most energetically difficult step, the 

 photolysis of water, has yet to occur, we will suppose that the 

 new form of the quantum converter would then react with water 

 to produce a reducing agent and some form of hydroxyl or per- 

 oxide compound which can ultimately liberate oxygen. A 

 requirement for this reaction is that the resulting bond energies 



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