LECTURE VI. 



FATS LECITHIN CHOLESTEROL. 



AMONG the foods of the animal organism, the fats occupy a peculiarly 

 important place, due to their high calorific value. They also play an 

 important role in the plant, and especially in the animal kingdom, as 

 reserve material. The animal organism stores tremendous reserves of 

 vital energy in the form of fats. 



The most important locations are the intermuscular connective tissue, 

 the fatty tissues of the abdominal cavity, and the subcutaneous connective 

 tissue. Small deposits occur in every organ and cell. These fat reserves 

 vary much in size, depending on nutritive conditions, so that no definite 

 statement can be made regarding the fat content of the individual organs. 



In the vegetable kingdom the fats are also widely distributed, and act as 

 reserve stores, yet never to the same extent as in the animal organism. 

 Fats are deposited in dormant parts, as in seeds, in which we first find 

 the accumulations of carbohydrates, then fats; often they occur together. 

 Here the fat does not occur in the form in which we meet it in the animal 

 tissues. It is very finely disseminated throughout th'e protoplasm, only in 

 isolated cases occurring deposited as crystalline aggregates in the nutritive 

 cells. Supplies of fat have occasionally been found in stalks embedded 

 in the soil; onions, tubers, and roots, and similiarly the shoots and branches 

 of bushes in winter as well as the leaves of evergreen have shown a reserve 

 supply of fat. 



The fats are composed entirely of the elements carbon, hydrogen, and 

 oxygen. The natural fats belong to the group of neutral fats. Free fatty 

 acids are found only in small quantities. The neutral fats are, in general, 

 to be considered * as esters of glycerol and monobasic fatty acids; i.e., in 

 the triatomic alcohol, glycerol, the hydrogen atoms in all three hydroxyl 

 groups are substituted by fatty acid-radicals (R) : 



CH 2 . R 

 CHO .R 



CH 2 O . R 



Glycerol Fatty acid 

 residue radical 



Cf. Chevreul: Chem. Untersuchungen iiber Tierische Fette. Paris, 1823. 



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