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organic compounds almost quantitatively into carbon dioxide and 

 methane. This occurred with such an utter independence of the 

 nature of the substrate that this fermentation could justifiably be sum- 

 marized in the following general equation : 



CH.O. + (n- f - |) H a O -. (| -f + |) CO, + £ + |-|) CH 4 



It would take too long to dwell upon the progress made with regard 

 to our insight into the mechanism of the various fermentation proc- 

 esses. I need only remark that nowadays we know that these gross 

 elementary processes in reality consist of long chains of primary, as a 

 rule reversible, reactions, each of which is promoted by a specific 

 catalyst. The well-known scheme of alcoholic fermentation may be 

 given here by way of example (Table V). 



The most remarkable feature of the scheme as a whole is undoubt- 

 edly that the primary reactions evidently belong to two reaction types : 

 we are dealing either with the transference of a phosphate group from 

 one molecule to a second one, or with a coupled dehydrogenation and 

 hydrogenation. Another point worth noticing is that the fermentation 

 of one molecule of glucose is indissolubly connected with the formation 

 of two molecules of adenosine triphosphate (ATP) out of two mole- 

 cules of adenosine diphosphate (ADP). This implies the coupling of 

 the sugar fermentation with the stoichiometric consumption of a second 

 compound. 



I shall return to this point later, and wish to remark first that all 

 that has become known about the other sugar fermentation processes 

 agrees with the idea that these too can be reduced to chains of trans- 

 phosphorylations and transhydrogenations. The same has now been 

 found to hold for the chemistry of the normal respiration process in 

 which glucose is oxidized to carbon dioxide and water (Table VI). 



Here it is generally accepted nowadays that the initial conversions 

 which the glucose molecule undergoes are the same as in alcoholic 

 fermentation. However, the pyruvic acid in a complex reaction in- 

 volving a dehydrogenation is coupled with oxalacetic acid, and in 

 doing so enters the Krebs or tricarboxylic cycle, where four more 

 dehydrogenations occur, and at the end of which oxalacetic acid is 

 regenerated. 



It should be remarked by the way that the respiratory chain is also 



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