RESPIRATION OF PLANTS 99 



and cause an abundant formation of one of these products. 

 By the introduction of sodium bisulphite which combines with 

 acetaldehyde, large quantities of glycerin may be accumulated. 

 This method is being widely applied in industry for the produc- 

 tion of glycerin by the use of carbohydrates as a source instead 

 of fats. 



A fact of great interest is the participation of phosphoric acid 

 in the reactions of fermentation. It has been proved that phos- 

 phates greatly accelerate the fermentation of sugars, sometimes 

 as much as ten to twenty times, especially in the case of fermenta- 

 tion being produced not by living yeast but by the enzyme 

 zymase. Phosphoric acid therefore is designated by many 

 authors as the coenzyme of alcoholic fermentation. The 

 investigations of Ivanov (1905) and Harden and Young (1905) 

 have shown that in the first stages of fermentation a diphosphoric 

 ester of fructose, C6Hii04(Na2P04)2, is formed, the so-called 

 ^'zymophosphate," this synthesis being assisted by a special 

 enzyme phosphatase. With the further course of fermentation, 

 the hexose diphosphate disintegrates under the influence of the 

 hydrolytic enzyme, phosphatase always producing fructose 

 regardless of the kind of hexose from which it was formed origin- 

 ally. The cause of such an accelerating effect of phosphatase 

 on fermentation is not entirely clear. It is possible that the 

 transformation of all kinds of hexoses into fructose may be 

 somehow connected with the existence of a special unstable mod- 

 ification, the so-called ''gamma" (7) fructose, which according 

 to recent data is the most active sugar, participating in all vital 

 processes. It is postulated as having the following structure: 



HOCH2COH CHCH2OH 



OHCH — HCOH 



Other sugars, hexoses as well as pentoses, give a similar 

 7 form, and it is in this unstable form that they react most 

 easily. It is interesting to note that in the molecule of sucrose, 

 fructose is present in an active form and in the case of inversion 



