Lipide metabolism 



19 



An appreciable portion of the body weight of a normal animal can 

 be attributed to the presence of lipides. For example, 10 per cent or 

 more of the body weight of a mammal is due to lipides, the majority 

 of which is in the form of fats. As was stated in Chapter 13, body 

 lipides are distributed in varying amounts in all organs and are stored 

 in highly specialized connective tissue called depots. In these depots, 

 a large part of the cytoplasm of the cells is replaced by droplets of 

 lipide. 



Body lipides serve as an important source of potential chemical 

 energy. Each gram of fat, for example, yields more than twice as 

 many calories as an equivalent weight of carbohydrate or protein. 

 Moreover, the normal animal contains a greater quantity of easily 

 mobilizable lipide than of carbohydrate or protein. In times of nutri- 

 tional insufficiency, an animal can meet the endergonic requirements 

 necessary for the maintenance of life by drawing on its lipide depots 

 for reserve energy. Other functions of depot lipides are listed in 

 Chapter 13. 



FAT CATABOLISM 



In anabolism, the liver serves as a temporary storage organ for fat 

 while phosphorylation (phospholipide formation) is taking place. The 

 phospholipides serve as the principal form in which fat is transported 



453 



