CHEMICAL PHENOMENA IN LIFE 



three large groups of enzymes : enzymes in the 

 service of the assimilation of food and of digestion, 

 enzymes employed in respiration, and those 

 employed in dissimilating processes partly forming 

 the so-called end-products of metabolism. We 

 may maintain that all decomposing processes 

 connected with the assimilation of food are ruled by 

 enzyme reactions. The end of all these reactions 

 is to form from the substances occurring in food 

 the primitive stem-substance, such as glucose 

 from the carbohydrates or amino-acids from 

 albuminous substances. Each cell contains such 

 enzymes, and is able to reconstruct its substances 

 from the fundamental organic groups which are 

 formed from the food by a host of enzyme re- 

 actions. In consequence of this, each cell is able 

 to rebuild its own specific albumin from the food, 

 and does not take up the albuminous substances 

 as they are present in the food without any change. 

 We therefore distinguish two stages in the digestion 

 and assimilation of food. One stage is merely 

 analytical, a splitting stage. Here the different 

 hydrolytic enzymes, such as Upases, amylase, 

 saccharase, maltase, the proteases, develop their 

 activity. In the following stage the reconstruction 

 of cell-substance takes place, the synthesis of 

 the organic principles of life. Modern chemistry 

 has been fortunate enough to obtain even here 

 remarkable results from experiments. 

 We should remember that hydrolytic processes 



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