572 



A. A. Benson 



H2C0H 



HgC-SOs 



H2C0H 



O-CHz 



HC0-C0-C|7H29 

 H2CO-CO-C17H29 



-CHg 



HCO-CO-C17H29 

 HgCO-CO-CgHji 



p— CHz 



HC0-C0-C|7H29 



H2C0-C0-C,7H29 



Fig. 1. Glycolipids of chloroplasts. Galactosyl diglyceride, 

 the plant sulfolipid ( sulfoquinovosyl diglyceride), and digal- 

 actosyl diglyceride. 



is the "neutral lipid" to which Menke^ referred in his early analysis of 

 chloroplast lipids. The water -solubility of the galactosyl groups, coup- 

 led with the hydrophobic and liquid properties of the two tri -unsaturated 

 C18 fatty esters (linolenic acid), gives these lipids their surfactant pro- 

 perties. They resemble the synthetic non-ionic detergents. The moder- 

 ate water -solubility of the galactolipids allows one to consider their dif- 

 fusion or transport in the aqueous phase. Yet, it is not so great as to 

 preclude formation of stable myelin figures when the pure digalactosyl 

 diglyceride is exposed to water. 



The most striking aspect of the galactolipids is their phenomenal 

 fatty acid composition. They are the most unsaturated lipids in Nature 

 and contain as much as 96% linolenic acid^*''^^'^ The sulfolipid^ and 

 phospholipids^^ on the other hand,possess saturated as well as unsat- 

 urated acids. Fatty acid compositions of glycolipids isolated from 

 alfalfa and Chlorella are given in Table I. 



Table I 

 Fatty Acid Composition of Glycolipids of Alfalfa and Chlorella^ 



Monogalactolipid 



Sulfolipid 



Digalactolipid 



Alfalfa 



Chlorella 



