lyo ORGANIC AGRICULTURAL CHEMISTRY 



The Small Intestine 



The digestion of carbohydrate food beginning in the mouth 

 and ceasing in the stomach is taken up again when the food 

 reaches the small intestine. The action of the salivary enzymes 

 has been completely destroyed, and the action which is taken 

 up again in the small intestine is due to new enzymes. 



Pancreatic Juice. Amylopsin. — The first enzyme acting on 

 carbohydrate food in the intestine is the starch-hydrolyzing 

 enzyme amylopsin. This enzyme is present in the pancreatic 

 juice which flows into the intestine from the pancreas very near 

 the opening from the stomach into the intestine. The action 

 of amylopsin is exactly like that of ptyalin, i.e. it hydrolyzes 

 starch to maltose through the intermediate stages of dextrin 

 and iso-maltose. It is, however, more active than ptyalin. 

 The pancreatic juice is like the saliva in being alkaline. in re- 

 action and the amylopsin, like ptyalin, acts best in this medium. 

 Any starch or dextrin food which is undigested by the action 

 of ptyalin of the saliva is acted upon in the intestine by the 

 amylopsin and the resulting product is maltose. Thus, when 

 the carbohydrate food materials have been acted upon by both 

 ptyalin and amylopsin, it contains only the following sub- 

 stances : (a) monosaccharoses, originally present in the food, 

 and some glucose formed from maltose by the action of maltase 

 in the saliva, (b) disaccharoses, cane sugar and milk sugar, 

 originally present in the food and malt sugar in the food or 

 formed from polysaccharoses by the action of ptyalin and 

 amylopsin. The monosaccharoses now present in the food 

 mass need no further digestion. The disaccharoses, however, 

 all need to be hydrolyzed to monosaccharoses before digestion 

 is complete. It is interesting to note that amylopsin is not 

 present in the pancreatic juice of infants for the first few weeks 

 after birth, which explains their inability to digest starch. 



Intestinal Juice. — The hydrolysis of the three disaccharoses 

 is accomplished by three enzymes which are present in the 

 intestinal juice secreted by the cells of the mucous lining of the 



