CHAPTEB LXXIX 

 PAT METABOLISM (Cont'd 



Two very important questions of fatty-acid metabolism may now be 

 considered: namely, (1) how is fatty acid formed (rum carbohydrate? 

 and (2) what becomes of the fragments into which thi fatty-acid molecuh 

 is split as the result of thi desaturation process? Although these prob- 

 lems involve chemical details of a somewhal complex nature, we must 

 not on lliis account fail to consider them; for, as we shall Bee, much of 

 what is known has an importanl practical application depending on the 

 fact that certain of the intermediary substances may accumulate in the 

 organism and develop a toxic action. 



The Production of Fatty Acid out of Carbohydrate. If we place the 

 formulas for glucose and palmitic acid side by side, thus: 



CH,0H-(CH0H) 4 -CH0 (glucose), and 

 CH 3 - (CH,) M -OOOH (palmitic ari.l) ; 



we shall sec that this transformation must involve: (1) a considerable 

 alteration in the structure of the molecule, (2) the removal of oxygen, 



and (3) the fusion of several glucose molecules into our molecule of fatty 

 acid. 



The conversion of carbohydrate to fa1 therefore involves a process of 

 reduction, and the resulting molecule must be capable of yielding more 

 energy when it is oxidized than the original one of carbohydrate, for 

 obviously the system 8 - CH 2 (which corresponds 1«> fat) will d 

 more energy than thai of 0, CHO I which corresponds to carbohydrate 

 just as a piece of wood when it is burned will develop more heat than ;i 

 piece of charcoal. This explains why one gram of fat yields 9.3 calories 

 of heat, and one gram of carbohydrate, only 4.1 (page Patty 



acid therefore contains more potential energy than sugar, and in explain- 

 ing its synthesis from BUgar in the animal body We must indicate 



sourci of tin extra energy. Tins is dependent on oxidation of Borne Bug 

 molecules which do not themselves become changed to fatty acid 

 proceeding side bj side with the reduction which affects the others and 

 represented in the outcome of the reaction by the combustion products 



CO, and II. <>. thus: 



M •• 13 20 CO C 16 H„0 20H,0 



gll BC itty acid 



707 



