CHAPTEH l.\ 

 THE BIOCHEMICAL PRO) ESSES OF DIGESTION 



In a book designed primarily for clinical workers, it would be ou1 

 place to enter into details concerning the biochemical proc< taking 



place during the digestive process. There is, however, a certain amount 

 of fundamental knowledge which it is essential thai we should consider. 

 In the firs1 place it should be borne in mind that in the digestion 

 carbohydrates and proteins, various intermediate stages are pas 

 through before the final absorption products are formed. Tin- highly 

 complex molecule of which protein, fur example, is composed, is I 

 of all broken down into several smaller bu1 still highly complex mole- 

 cules, each of which thou undergoes further disruption, until ultimately 

 the amino a<-ids are se1 free. Certain enzymes, such as trypsin, '-an 

 carry this process from the beginning through the - of its 



course without the assistan f other enzymes, hut in the natural proc- 

 ess «'f digestion, as it occurs in the gastrointestinal tract, the different 

 stages of the. disruption arc controlled by different enzymes. One enzj 



prepares the f 1 for action by the next. This interdepei the 



actions of the enzymes demands that some provision should be made 

 whereby each enzyme is secreted :;t the proper lime; that is, when the 

 foodstuff has already been prepared for its action by that of 'in prede- 



jor. Thus, it would he useless after food is taken for thi ic and 



pancreatic juices t<» he secreted at the same time. Instead, the gastric 

 juice is secreted first, and the pancreatic only after the food has 1 

 prepared \'^r its action. This correlation in function we have already 

 seen to he dependent largely on the action of hormi i 



DIGESTION IN THE STOMACH 



The gastric juice contains two important digestive agencies 1 

 enzyme, pepsin, and 2 hydrochloric acid. It is particularly in ju 

 secreted in the cardiac rw<\ of the stomach that these two subst 

 found present; towards the pyloric end the hydrochloi 

 disappears, and the pepsin content 1" distinctly less 



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