CHEMICAL COMPOSITION OF PLANTS 55 



most common is glutenin, which forms part of the gluten of 

 wheat. 



Proteins represent the most important and most characteristic 

 components of the Hving substance. They are absolutely indis- 

 pensable for the formation of protoplasm, and the analysis of 

 the protoplasm of a slime mold stated in Art. 9 shows that 

 quantitatively likewise they form one of its most important 

 parts. It would be erroneous to assume that life activity is 

 entirely dependent on the structure of the protein molecule, but 

 Stanley has recently shown that the crystallizable protein of 

 viruses has many properties similar to living substance. 



Lipoids and carbohydrates as well as electrolytes form a no 

 less indispensable component of the living protoplasm. Life 

 as a new quality, distinguishing organisms from lifeless bodies 

 and creating a number of new essential features, is connected 

 not with several separate groups of organic substances but with 

 the entire complex forming the protoplasm. Protein substances 

 isolated from this complex do not display all of the properties 

 of living su.bstance, of which a continuous metabolism is the 

 most important. Similar to starch or fat, reserve proteins, Hke 

 edestin or gliadin, when extracted from the cell represent only 

 materials for the structure of living protoplasm. 



13. Hydrolytic Decomposition of Reserve Carbohydrates and 

 Fats during Germination of Seeds. Enzymes Accomplishing 

 This Decomposition. — The group of substances examined above 

 is capable of remaining permanently unchanged only in com- 

 pletely dry and dormant seeds. For this reason, seeds furnish a 

 highly convenient material for obtaining and studying these 

 substances. As soon as live seeds are moistened, a series of 

 complex biochemical processes is initiated. These processes 

 represent the initial stages of germination and permit the growth 

 and development of the seed embryo by using the reserves stored 

 in the cotyledons and other storage organs. The most charac- 

 teristic feature of these processes is the decomposition of 

 comphcated storage substances into their components. Polysac- 

 charides usually disintegrate into monosaccharides, fats into 

 fatty acids and glycerin, and proteins into amino acids and 

 ammonia. All these reactions of disintegration proceed with an 

 addition of water and are of the general type of hydrolytic 

 reactions. 



