ENERGY SUPPLY OF THE CELL 



141 



In the first case, if fermentation ceases through lack 

 of fermentable material, there is not much to be said 

 concerning the endpoint. It will be in proportion to the 

 amount of fermentable material present, and we can 

 easily compute the maximum amount of fermentation 

 products if we know the initial concentration of the 

 substrate. We know, that from 1 gm. of sugar, we cannot 

 possibly expect more than 0.49 gm. CO2 in an alcoholic 

 fermentation. The few experiments in dilute solutions 

 with which the writer is familiar, indicate that the 

 amount of CO2 or alcohol is considerably less than should 

 be expected, and this is probably due to the utilization 

 of a comparatively large amount of fermentable material 

 for cell construction in a poor medium. This may not 

 be the case, however, if an abundance of non-fermentable 

 construction material is supplied while the fermentable 

 material is scarce. 



More important and more interesting is the question 

 of the endpoint of fermentation when an excess of 

 fermentable material is present, and the fermentation 



Table 28. — Influence of the Sugar Concentration upon the 



Endpoint of Fermentation of Streptococci in Peptone Solution 



(Numbers mean per cents of lactic acid formed) 



ceases before all of it is consumed. Since we are dealing 

 with enzyme reactions it seems logical to discuss first 



