MONOUNSATURATED FATTY ACIDS 



59 



250 



200 



150 



palmitoleic acid 



plus Tween 40, o 



cjs-vaccenic acid 

 plus Tween 



100 



0.5 



Fig. 3.2. Fatty acid growth curves for L. arabinosus. Abscissa, /^moles 

 of fatty acid per tube. Ordinate, Klett readings. 



ing from one another by successive 2-carbon shortening 

 of the chain was available for study. The position of the 

 double bond with respect to the methyl group was kept 

 constant in this series of acids. 



The ability of the organisms studied to utilize unsaturated 

 cis acids possessing carbon chains shorter than cw-vaccenic 

 acid (Figs. 3.2, 3.3, and 3.4) lends support to the hypothesis 

 that unsaturated fatty acid biosynthesis may involve elonga- 

 tion of the carbon chain of a shorter chain unsaturated 

 precursor. However, the short-chain acids may substitute 



