[Bbitish Association Report, 1922. 



Addendum, p. 396. The following should be added to the Discussion on 



Fhotosynthesis : 



(/) Prof. M. C. Potter. — Photosynthesis: Electric Energy. 



In addition to the calories set free during the fermentation of sucrose and 

 glucose by yeast, there is also a liberation of E.M.F. of approximately .3 volts 

 to .5 volts.' Thus the equations should express this E.M.F. as well as the 

 difference of calories : 



CiaHasOn + H^O = 4C2H5OH + 4CO2. 

 1352.7 cal. 4 (326.7) cal. 



The equation should therefore read : 



CiaHaaOn + H^O = 4C,H,0H + 4CO.2 + 49.9 cal. + x (E.M.F.), 



where x is a constant at present undetermined, but .3 volts are obtained during 

 the fermentation. 



A similar phenomenon necessarily enters into enzyme action : 



Sucrose Dextrose Laevulose 



Ci2H2.,0,i + H.,0 = CeH.^Os + CgHi^Oe. 



1352.7 cal. 673.7 cal. 675.9 cal. 



During this reaction .03 volts are obtained, and the equation should be expressed : 



C12H.22O11 + H2O = CeHiaOe + GgiLnOe + 3.1 cal. + x (E.M.F.). 



The amount of electricity has not at present been determined, but it would 

 appear to bear some definite relation to the calories. 



It may be suggested that as the atom is built up of electrons and protons, 

 so must these also form part of the structure of the molecule. This E.M.F. 

 therefore expresses the difference between the electrons and protons in the 

 various molecules, just as the calories express the difference between their heats 

 of combustion. 



It may be noted that the action of the enzyme is from a higher potential 

 to a lower one, and that during the reaction energy is liberated. For an enzyme 

 to act synthetically energy must be supplied for the work performed, and hence 

 it is improbable that synthetic enzymes exist. 



The view is put forward that electrons and protons form an integral part 

 of the carbohydrate, and are required during the synthesis of these bodies (and 

 all intermediate ones), and that they may be found to be a limiting factor in 

 photosynthesis ; and further, that there may be endo-electric and ex-electric 

 reactions analogous to the endothermic and exothermic reactions. 



' Pror.. Roy. Soc, B, vol. 84, 1911. 



