390 



Photosynthesis 



phyll molecule to the photolyte molecule, since we now know that the light acts 

 within the same molecule that absorbs it. The light reaction of photosynthesis is 

 thus nothing eise than the photodissociation of a pigment, comparable to the photo- 

 dissociation of carbon monoxide-hemin Compounds, and the quantum yield of 1 

 is almost self-evident. 



Upon adding the three equations of the reaction sequence, the photolyte is 

 eliminated, and the net result is the Splitting of carbonic acid by 3 quanta of light, 

 which is what one finds experimentally in the balance of photosynthesis. 



Nothing seems to be simpler than this Solution of the quantum problem. Of the 

 110,000 calories that are necessary for the Splitting of 1 mole of carbonic acid, 



Fig. 5. Vessel for demon- 

 stration of the necessity 

 of respiration for photo- 

 synthesis. 



100 



90 

 J0 



ho 



Z60 



50 

 .40 



30 

 20 

 10 



4 8 12 16 20 24 



MM0 2 PRESSURE (MMOF WATER) 



Fig. 6. Respiration and photosynthesis at 

 low pressures of CK 



70,000 are provided by a respiratory process. The remaining 40,000 calories that 

 the light provides is exactly the amount of energy of 1 mole quanta of red light. All 

 quantum difficulties are thus eliminated. 



In order fully to appreciate this Solution, one must reflect that in photosynthesis 

 no energy would be gained, but rather lost, if the energy of the respiratory process 

 were taken from the energy störe of the cells. Only because the respiratory energy 

 of reaction 2 is directly supplied by light is a net gain of energy attained. All detail 

 is simple physics and chemistry. But the whole is a higher kind of physics and 

 chemistry, devised by the genius of living nature. 



To conclude the discussion of energetics, I would like to describe an experiment 

 that ought to be demonstra'ced to all students of biochemistry, because it confirms 

 in the simplest possible way the requirement of our equations that there is no 

 photosynthesis without respiration. 



Figure 5 shows the experi mental vessel that is to be attached to a manometer. 



