CHAPTER LV1 

 THE BIOCHEMICAL PROCESSES OF DIGESTION Cont'd 



DIGESTION IN THE INTESTINES 



The further changes which the half-digested foodstuffs in the chyme 

 undergo in the intestinal canal depend on the enzymes present in 

 secretion of the various glands and on the pn of bacteria, 'i 



must importanl of the digestive juices are the pancreatic juice and Idle 

 The latter, however, does not contain any enzyme, its influence on * 1 i _ 

 tion being entirely adjuvant. 



Pancreatic Digestion 



When we were considering the mechanism of secretion of the pon- 

 tic juice, we saw thai the juice produced by the action o eth 

 the gland cells does no1 contain any active proteolytic enzyme, although 

 it contains one capable of acting on polysaccharides and another, on fat. 



The Action of Trypsin 



When pancreatic juice is mixed with the secretion of the duodenum or 

 the upper pari of the small intestine, it immediately develops powerful 

 proteolytic power. The same resull may also be obtained by mixing it 

 with an extract of the mucous membrane of the duodenum made with 

 dilute bicarbonate solution. A very small amounl of ti tract is 



capable of increasing the digestive activity of a very considerable quan- 

 tity of pancreatic juice, showing thai the action depends on the presence 



of an enzyme which has been called enterol This inline: 



intestinal secretion is readily destroyed by heating. 

 Large quantities of alkali are contained in the pancreatic juice and 



bile, so that in the upper reaches of the intestine the acidity of the 



chyme is practically neutralized. A little lower down, however, an acid 

 reaction may again devel< On account of these fact* 



has been concluded that the activity of trypsin is most rapid in the p 

 ence of a slighl e\crss of hydroxy] ions; i.e.. in a weakly alkaline solu- 

 tion. It is interesting to note that, as a resull of th< 

 alkali by the pancreas, extracts of tl jan af - iw a v< 



1 1 i >_r 1 1 degree of acidity in comparison with extract m oth( 



