ALBERT SZENT-GYORGYI 9 



tic scale by many niillions of years. These chroniatophores are still 

 very far from the origin of life, but this is as far as we can go in this 

 direction at present, so a lew remarks on these chroniatophores may 

 be permitted. As mentioned earlier, the electrons go round in them 

 in a relatively simple closed circle, going from chlorophyll to quinone, 

 from quinone to a cytochrome, and from cytochrome back to chloro- 

 phyll. The electrons seem to go it one by one. In any case, they are 

 excited one by one. They are also transmitted one by one from 

 cytochrome to chlorophyll, which makes it most probable that the 

 whole circle is a one-electron business. As to the mechanism of this 

 passage of the electron we know from experiments of Commoner and 

 Calvin that the illuminated chloroplasts give an electron spin 

 resonance signal. This means that an electron pair has been un- 

 coupled, a purely physical process. It has also been discovered lately 

 by Chance and Nishimura that when cells of the photosynthetic sul- 

 fur bacterium, Chromatium are illuminated at liquid Ng tempera- 

 tures, cytochromes become oxidized, suggesting that in chroniato- 

 phores electrons pass from cytochrome to chlorophyll. This means 

 that no diffusion or classic chemical reaction is involved. It seems 

 highly probable that the whole circle consists only of quantum me- 

 chanical changes, physics and no chemistry, that is, no collisions and 

 rearrangement of covalent bonds. It involves physical concepts, as 

 molecular excitation, semiconduction, n-p junctions, charge trans- 

 fer, etc. A single electron, passing from one orbital to the other, 

 is not expected to cause any major rearrangement in bond structure. 

 I have personal reasons to emphasize this point. My own problem 

 is: how is the animal body driven? How does it produce the various 

 forms of work, w, mechanic, electric, or osmotic, the w's by which we 

 know life from death. My research has always been led by the con- 

 viction that the whole of living Nature is built on but a very few 

 basic principles. Accordingly, I find that my own body reflects the 

 same basic principles by which life was driven at its beginning. I take 

 my energy from the plants, mainly in the form of fat and carbo- 

 hydrate. What I do with these is to take off their H atoms, and put 

 them on TPN or DPN and send down electrons over riboflavin and 

 cytochromes in the oxidative chain, as the bacterial chroma tophores 

 do, producing ATP by the energy of the dropping electron which 

 reaches its lowest level on the Oo, released in the open circles of 

 photosynthesis. I also strongly believe that ATP has two different 

 functions in my body. The one is to supply energy for endergonic 

 synthesis. This it does by "group transfer," that is, by transmitting its 



