CLASSIFICATION 5 



(b) Glucolipids. These substances, first isolated from the spleen in 

 Gaucher's disease, were shown to contain glucose in place of galactose,'^ 

 but the other components, viz., sphingosine and a lignoceric acid derivative, 

 were similar to those found as galactolipids. 



c. Sulfolipids. These contain a sulfate radicle. 



(3) Derived Lipids 



This class includes derivatives of the first two classes of lipids obtained 

 l)y hych'olysis which still retain the lipid characteristic of solubility in ether, 

 etc., and insolubility in water. This class contains the important compo- 

 nents of the so-called non-saponifiable extract or non-saponifiable fraction 

 (NSF). 



a. Fatty Acids. This group includes all fatty acids obtained from 

 natural products which are soluble in fat solvents and which are insoluble 

 in water. The fatty acids starting with caprylic acid (CH3(CH2)6COOH) 

 and the higher ones belong in this categoiy. Such fatty acid derivatives as 

 soaps are not considered to be members of this group. 



b. Alcohols. The alcohols of higher molecular weight which are ob- 

 tained by hydrolysis of waxes and which are insoluble in water belong 

 in this category. Glycerol is water-soluble and hence is not included. 

 These alcohols may be classified as f ollow\s : 



(a) Straight-Chain Alcohols. The common representatives are cetyl (or 

 palmityl), CH3(CH2)i4CH20H; octadecyl (or steryl), CH3(CH2)i6CH20H; 

 ceryl, CH3(CH2)24CH20H; and myricyl (or melissyl), CH3(CH2)28CH20H. 



(b) Sterols. These all contain the steroid nucleus (cyclopentanophenan- 

 threne). The commonest are cholesterol, which is obtained from animal 

 fats and the phytosterols, sitosterol, and stigmasterol, present in the vege- 

 table oils of the higher plants or phanerogams. Ergosterol, which is a 

 sterol characterizing a lower order of plants (cryptogams) , is also a member 

 of this group. 



(c) Alcohols Containing the ^-lonone Ring. These include vitamin A itself 

 and such carotenols as cryptoxanthin, lutein, and zeaxanthin. 



c. Hydrocarbons. This group includes products which contain no 

 alcohol groups and which cannot be saponified. Several classes of hydro- 

 carbons can be distinguished, as follows: 



(a) Aliphatic Hydrocarbons. This group includes iso-octadecane (Cis- 

 Hss), which is liquid and is found as a component of liver fats. There are 

 also a number of solid hydrocarbons which are largely found in beeswax 

 and plant waxes, such as pentacosane (CH3(CH2)23CH3) and homologues 

 up to hentriacontane (C31H64). 



'^ N. Hallidav, H. J. Deuel, Jr., L. J. Tragerman, and W. E. Ward, J. Biol Chem., 1S2, 

 171-180 (1940). 



