CHAPTER III 



THE OXIDATION AND METABOLISM 



OF TRIGLYCERIDES, FATTY ACIDS, 



AND GLYCEROL IN THE ANIMAL BODY 



1. Introduction 



Under normal conditions, fats are completely oxidized in animals to 

 carbon dioxide and water; approximately nine Calories of heat are lib- 

 erated per g. of fat broken down. It is now known that the fatty acids 

 and glycerol have different pathways of oxidation. In the case of the 

 fatty acids, the degradation involves a series of reactions by which the 

 fatty acid chain is broken down by two carbon units at a time. There 

 is increasing evidence that the processes of synthesis and oxidation of fatty 

 acids represent reversible phases of the same reaction. The understanding 

 of the subject of fat oxidation has been greatly facilitated by the fact that, 

 under conditions of fasting, or in such metabolic disorders as diabetes, the 

 ketone bodies are excreted without being oxidized to carbon dioxide and 

 water. It is generally agreed that glycerol is first converted to glucose, 

 after which its metabolic fate parallels that of glucose. 



The general subject of fat oxidation has been reviewed by Breusch^ and 

 by Stadie,- while Lehninger^ summarized the work on enzymic oxidation of 

 fatty acids. 



2. The Oxidation of Triglycerides and Fatty Acids 



(/) Methods and Theories of Fat Oxidation 



Several theories have been advanced to explain the mechanism of 

 oxidation of fats. These are all concerned with the oxidation of fatty 

 acids, since the preliminary change in the oxidation of triglycerides prob- 



1 F. L. Breusch, Advances in Enzymol., 8, 343-423 (1948). 



2 W. C. Stadie, Physiol. Revs., 25, 395-441 (1945). 



^ A. L. Lehninger, Enzymic Oxidation of Fatty Acids, in R. T. Williams, Lipid 

 Metabolism, Biochem. Soc. Symposia, No. 9, Cambridge Univ. Press, 66-79 (1952). 



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