TYPES OF RESPIRATION 61 



The complexity of the respiratory reactions, as they have just 

 been presented, indicates only a portion of the misconception that is 

 conveyed by the formal expression for fermentation: C 6 Hi 2 Oe -» 

 2C 2 H r ,OH + 2CO L ». This point is further emphasized by the 

 following data of Rubner [Lutman (1929)1 on the products of 

 fermentation by yeast of 100 grams of sucrose and the caloric 

 value of the products formed: 



Kg-cal Value 



51.1 grams alcohol 358.36 

 3.4 grams glycerin 14.38 

 0.65 grams succinic acid 1.99 

 1.3 grams miscellaneous products 5.15 



49.2 grams carbon dioxide 0.00 



Total Kg-cal value 379.88 



Kg-cal value, 100 grams sucrose 396.80 



Energy released, Kg-cal 16.92 



According to the sugar-phosphate theory, some phosphate, 

 such as that of sodium or potassium, is necessary in alcoholic 

 fermentation. The phosphate reacts with the hexose to give a 

 diphosphoric acid ester. Apparently the phosphate is not a co- 

 enzyme to make possible the working of zymase, but it acts as a 

 catalytic agent. The formation of the diphosphoric acid ester is 

 accompanied pari passu by a second reaction that again liberates 

 the phosphate and the hexose. These reactions may be expressed 

 as follows: 



a. 2C 6 H 12 6 + 2R 2 HP0 4 + Zymase -> 



Hexose Phosphate 



2C0 2 + 2C 2 H 5 OH + 2H 2 + C 6 H 10 O 4 (PO 4 R 2 ) 2 



Alcohol Glucose di- 



phosphate 



b. C 6 H 10 O 4 (PO 4 R 2 )2 + H 2 -> C 6 H 12 6 + 2R 2 HP0 4 



According to Meyerhof and Kiessling (1935), the hexose and 

 phosphate react to form both glucose monophosphate and glu- 

 cose diphosphate. Then by oxidation-reduction the monophos- 

 phate becomes a molecule of glyceric aldehyde phosphoric ester 

 and one of glyceric aldehyde, and the glucose becomes two mole- 

 cules of glyceric aldehyde phosphoric ester. As a next step, the 

 glyceric aldehyde phosphoric esters are hydrolyzed to glyceric 

 aldehyde, and phosphate is again freed. The glyceric aldehyde 



