52 Suggcstions to Teachers of Biochemisfry [Sept 



A PROPOSED CLASSIFICATION OF LIPINS 



LiPINS ARE ORGANIC SUBSTANCES OF WIDE BIOLOGICAL DISTRIBUTION. In PRAC- 

 TICALLY ALL CASES THEY ARE INSOLUBLE IN CONCENTRATED NEUTRAL SALINE SOLU- 

 TIONS. ThEY ARE SOLUBLE IN HOT ALCOHOL CR IN WARM ETHER, DR, AS IS USUALLY 

 THE GASE, IN BOTH SOLVENTE. 



I. Natural aliphatic lipins 



A. SIMPLE LIPINS. Natural aliphatic fats, waxes, soaps, and also the acids 



and alcohols (except glycerol) represented in them. Excepting the 



alcohols, these Compounds yield soaps with hot concentrated Solutions of 



caustic alkali, or alcoholate, or both. All of these substances contain 



carbon, hydrogen and oxygen, but are free from phosphorus, sulfur and 



nitrogen. (Ammonium soaps are exceptions, of course, in the matter of 



nitrogen content.) 



o. Fatty ACIDS, such as butyric acid and palmitic acid (formic and acetic 



acids excepted) ; various unsaturated acids, such as oleic acid and 



linoleic acid; and hydroxy acids of all these types. 



b. Salts AND ESTERS of the aliphatic acids comprising Group I, A, a. 



1. Soaps. Inorganic salts, such as potassium caproate and sodium 



stearate. 



2. Waxes. Esters of aliphatic mono-hydroxy and di-hydroxy alco- 



hols, such as cetyl palmitate (in spermaceti wax) and myricyl pal- 

 mitate (in beeswax). (See Group II, B — carhocyclic esters.) 



3. Fats and fatty ("fixed") oils — " Glycerides " : Esters of the tri- 



hydroxy alcohol, glycerol, such as tri-butyrin, tri-palmitin, and tri- 

 olein. 



c. Alcohols (mono-hydroxy and di-hydroxy) of the kinds obtainable from 



waxes, such as cetyl alcohol, carnaubyl alcohol, and myricyl alcohol. 



B. CONJUGATE LIPINS. Natural Compounds of simple lipins with non-lipin 



substances or radicals. All of these Compounds contain carbon, hydrogen 

 and oxygen ; and practically all of them contain nitrogen. These sub- 

 stances, with those in Group II, A, constitute the group of socalled 

 " lipoids " — a term without a definite chemical basis. (Protagon is a 

 mechanical mixture containing several conjugate lipins.) 



a. Proteolipins. Compound lipins containing protein radicals ("lecitho- 



proteins"), such as lecithalbumins and ovovitellins. (These products 

 may be mechanical mixtures of proteins and lipins.) 



b. Glycolipins. Compound lipins that are free from protein radicals, but 



which contain carbohydrate radicals, such as the " cerebro-galacto- 

 sids " represented by Phrenosin (" cerebron "). The substances in 

 this group are free from phosphorus. (Thudichum's " cerebrosids.") 

 (See Group I, B, d.) 



c. Phospholipins. Compound lipins that are free from protein and carbo- 



hydrate radicals, but which contain phosphoric acid radicals, such as 

 lecithin, cuorin and sphingomyelin. (Thudichum's "Phosphatids.") 



d. Glyco-phospholipins. Phospholipins which contain carbohydrate radicals, 



such as carnaubon and various phytolecithins. (Jecorin appears to be 

 a phospholipin-carbohydrate mixture.) 



