162 



II. DIGESTION AND ABSORPTION OF FATS 



a precursor for the phospholipid. 731 Finally, it is possible that the phos- 

 pholipid may be preformed in the intestinal cell and spread as a film on the 

 oil globule. In any event, the phospholipids in the intestinal cells would 

 be considered as terminal products rather than as intermediates in the syn- 

 thesis of fats. 



c. The Synthesis of Fats. The essential differences in the reactions oc- 

 curring in the intestinal cells as postulated in the Lipolytic and Partition 

 Theories are summarized in Table 19. 



Table 19 

 Comparative Explanations of Changes Occurring in the Intestinal Cells 

 Postulated in the Lipolytic and Partition Theories' 1 



Lipolytic theory 



Partition theory 



1. Resynthesis 



2. Phosphorylation 



3. Adrenal cortex 



Essential part of mechanism. 

 All fatty acid reconverted 

 to triglyceride 



A stage in resynthesis of tri- 

 glyceride fat b - c 



Essential for 

 phorylation* 



lormal phos- 



Not essential part of absorp- 

 tive mechanism 



Not concerned with resyn- 

 thesis. Occurs at oil/ 

 water interface, as an es- 

 sential change in inter- 

 facial structure and prob- 

 ably elsewhere** 



Not concerned in phosphory- 

 lation^ 



• A. C. Frazer, Physiol. Revs., 26, 103-119 (1946). 



b R. G. Sinclair, J. Biol. Chem., 82, 117-136 (1929). 



c R. G. Sinclair, Oil & Soap, 15, 70-74 (1938). 



d J. J. Elkes and A. C. Frazer, /. Physiol, 102, 24P-25P (1943). 



• F. Verzar and L. Laszt, Biochem. Z., 276, 11-16; 278, 396-400 (1935). 



f N. Stillman, C. Entenman, E. Anderson, and I. L. Chaikoff, Endocrinology, 31, 481- 

 485 (1942). 



The question as to whether or not triglycerides are normally synthesized 

 from fatty acids (or soaps) and glycerol in the intestinal cells is one of the 

 controversial phases of the problem of fat absorption. This concept 

 must be accepted if one agrees with the Lipolytic Theory of Bloor and 

 Verzar that fat is carried into the intestinal cell only after a complete hy- 

 drolysis of the triglyceride molecule has occurred in the small intestine. 

 On the other hand, if one believes the Partition Theory of Frazer, in which it 

 is postulated that fat is absorbed in particulate form, largely as triglyceride, 

 there is no need to assume a triglyceride synthesis in the epithelial cells. 



Frazer 645 discounts the fact that evidence of the presence of triglycerides 

 in the chyle after monoglycerides, fatty acids, or esters have been con- 



