80 



GENERAL BIOCHEMISTRY 



O 



CH2— O— C(CH.2),2— CHs 



CHOH 



O 



CH2— O— C(CH.2)]4— CH3 



l-niyristo-3-palniitiii 



o 



II 



CH.,— O— C(CH2)i2— CH3 



o 



11 



CH— O— C(CH2)i4— GH3 

 O 



CH2— O— C (GH2) 14— CH3 



l-myristo-2,3-dipalmitin 



o 



CH2— O— C(GH2) 12— CH3 



O 



II 

 GH— O— C(CH2)i4— GH3 



O 



GH2— O— C (GH2) 16— GH3 



1 -my risto-2-palmito-3-stearin 



Mixed glycerides also exist in several isomeric forms. A mixed di- 

 glyceride has three geometrically isomeric forms. A triglyceride such 

 as l-myristo-2,3-dipalmitin may occur in two isomeric forms, while a 

 triglyceride containing three different fatty acid residues can be 

 written structurally in three different ways. 



On the basis of our discussion of the various isomeric forms of 

 glycerides, one can predict that, if glycerol reacted randomly with 

 palmitic acid, 5 different glycerides (2 mono-, 2 di-, and 1 triglyceride) 

 could possibly be formed. Again, if glycerol reacted randomly with 

 palmitic and myristic acids, 17 different products might be formed. 

 Finally, if 3 different acids were esterified with glycerol in such a way 

 that all possible glycerides were produced, .39 products would be 

 included in the mixture. Thus an animal or vegetable fat which 

 yields 4, 5, or perhaps 6 or more different latly acids on hydrolysis 

 nuist be composed of an impressive number of different types and 

 isomeric forms of glycerides. This fact, in itself, accounts for the 

 relatively slow progress made in elucidating the precise chemical 

 structure of any one fat. 



