LIPIDES (fats and RELATED SUBSTANCES) 101 



in large amounts in brain and nerve tissue undoubtedly means that they 

 have an important function there. An unusual lipide type is represented 

 by the ylastnnlogens, substances first found in beef muscle, but also present 

 in brain. These lipidcs make up about 10 per cent of the total phos- 

 phatides of these tissues. Plasmalogen on hydrolysis gives rise to chola- 

 mine, a-glyccrophosphoric acid, and a higher aldehyde corresponding to 

 a common fatty acid, e.g., palmitaldehyde (C15H31CHO) or stearaldehyde 

 (C17H30CHO). Therefore, plasmalogens most probably have the follow- 

 ing formula, in which R represents the alkyl radical of a higher fatty acid. 



I ^CHR 



CHO^ O 



I II 



CH2— O— P— OCHoCHjNH, 



I ^ 



0- 



Plasmalogen 



Phospholipides containing inositol have been found in soybeans, as well 

 as in nerve tissue. One of the components of "brain cephalin" has been 

 found to be an alcohol-insoluble phospholipide which on hydrolysis gives 

 rise to equimolar portions of glycerol, a fatty acid, and inositol meta- 

 diphosphate: 



O 



H II 



^Cc::<)-P— (0H)2 



HCOH HCOH Q 



I I II 



HCOH„ HC-0-P(0H)2 



Inositol meta-diphosphate 



CEREBROSIDES (GLYCOLIPIDES) 



Compound lipidcs containing a sugar residue but no phosphorus are 

 present in relatively large amounts (7 per cent of the solid matter) in 

 brain tissue and probably occur in all organs of the body. These sub- 

 stances, called cerebrosides, are insoluble in ether and water, but dissolve 

 in pyridine or in hot alcohol. They are white solids which on hydrolysis 

 yield one molar erjuivalent each of a higher fatty acid {e.g., lignoceric) , 

 sphingosine or dihydrosphingosine, and galactose. Such a combination 

 of a carbohydrate, fatty acid, and base shows what unexpected com- 

 pounds exist in the body and demonstrates that the line between carbo- 

 hydrates, fats, and nitrogenous compounds is not nearly as sharp as 

 classifications might indicate. All the fatty acids which have been found 



