268 ESSENTIAL FATTY ACIDS 



X. Requirements 318 



A. Of Animals 318 



B. Of Human Beings 319 



I. Nomenclature and Formulas 



ROBERT S. HARRIS 



Accepted names: Essential fatty acids 



Obsolete name: Vitamin F 



Empirical formulas: Linoleic acid: C18H32O2 



Linolenic acid: C18H30O2 



Arachidonic acid: C20H32O2 

 Chemical names : Linoleic acid : A9 , 12-octadecadienoic acid 



Linolenic acid: A9 , 12 , 15-octadecatrienoic acid 



Arachidonic acid: A5 , 8 , 11 , 14-eicosatetraenoic acid 

 Structural formulas: 



CH3(CH2)4CH=CHCH2CH=CH(CH2)7COOH 

 Linoleic acid 



CH3CH2CH=CHCH2CH=CHCH2CH=CH(CH2)7COOH 



Linolenic acid 



CH3(CH2)4CH=CHCH2CH=CHCH2CH=CHCHoCH=CH(CH2)3COOH 



Arachidonic acid 



II. Chemistry 



RALPH T. HOLMAN 



Rigid exclusion of fat from an otherwise adequate diet of a variety of 

 animals results in the delayed appearance of a deficiency syndrome first 

 described in 1929 by Burr and Burr.^'^ This deficiency has been shown to be 

 caused by the lack of certain fatty acids which have come to be called the 

 essential fatty acids. Incorporation of these acids in the diet either pre- 

 vents or cures the deficiency symptoms. Although the fat deficiency 

 phenomenon parallels vitamin deficiency phenomena, the term vitamin 

 has not been generally applied to the essential fatty acids, probably be- 

 cause they are required in larger quantity than are most vitamins. 



Fatty acid deficiency and the essential fatty acids have been the subject 



^^ G. O. Burr and M. M. Burr, J. Biol. Chem. 82, 345 (1929). 



