12 GENERAL BIOLOGY 



The Carbohydrates (as also the Fats) lack the 

 nitrogen characteristic of protein. They contain 

 only carbon, hydrogen, and oxygen, the latter two 

 always present in the proportion found in water, 

 twice the number of hydrogen atoms as of oxygen. 

 They are simpler in structure than the proteins, but 

 like them may be combined into molecular aggre- 

 gates of higher degrees of complexity. The simple 

 sugars or monosaccharids, of which dextrose or glucose 

 is the most familiar, have the formula C 6 Hi 2 O 6 . 

 By combining two molecules of a monosaccharid 

 with the loss of a molecule of water l a disaccharid 

 may be formed, of which the most familiar example 

 is cane sugar (sucrose). Under the influence of 

 yeast a monosaccharid will break up into carbon 

 dioxide and alcohol, a process known as fermenta- 

 tion. By continuing the addition of monosaccharid 

 molecules, one to another, each time with the loss 

 of a molecule of water, more complex sugars, the 

 polysaccharids, are formed. These are the starches 

 and dextrines, and, most familiar of all, cellulose 

 and woody fiber. The ^carbohydrates in general 

 are more abundant in plants than in animals, al- 

 though one of them, glycogen, which is found abun- 

 dantly in the liver and muscles of higher animals, 

 is, of very great importance in animal nutrition. 



The Fats contain the same elements found in 

 the carbohydrates, C, H, and O, but in different 

 proportions and arrangements. In every case they 

 are the result of the combination of an acid with 



' C,H 12 0, + C 6 H 12 0, = 



