PRIMING REACTIONS 



187 



purpose, wished to assure their preservation by the addition of sugar and 

 he made an important observation : the mixture frothed and became rich 

 in alcohol. Alcoholic fermentation without cells had been discovered. Our 

 present knowledge of this phenomenon derives from elaboration of the 

 results of an experiment done by Harden and Young in 1906. Buchner 

 had observed that if one added phosphate to yeast juice, the COg production 

 was increased — for him this was the result of the change in acidity. 



10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 ISO 



TIME IN MINUTES 



Fig. 36 (Harden and Young) — Production of CO2 with time in yeast juice to which has 

 been added : a. glucose; b. the same mixture (25 ml of yeast juice + 25 mlof water in which 

 5g of glucose is dissolved) plus 5 ml of a 0-3M mixture of primary and secondary phos- 

 phates; c. a further addition of the same quantity of phosphates after 70 min. 



Harden and Young observed that after a temporary increase in COg 

 evolution, following the addition of phosphate, the effect died away, only 

 to be renewed on a further addition of phosphate. Moreover, successive 

 additions of phosphate led to a production of one mole of COg for each mole 

 of phosphate added and the increase in the production of alcohol corre- 

 sponded mole for mole to the amount of CO2 produced (Fig. 36). 



When Harden and Young sought the phosphate which they had added, 

 they found that it was not in its free form but was bound as phosphoric 



