COLLOID CHEMISTRY OF THE PROTEINS 



CHAPTER I 



COLLOID CHEMISTRY AND THE GENERAL 

 CHEMISTRY OF THE PROTEINS 



* 



IT would be superfluous to discuss which of the constituents 

 of the living cell are most important in vital processes. Proteins, 

 lipoids, and certain inorganic salts are alike indispensable, and 

 have a very intimate relation, both physical and chemical, one 

 to another. There is, however, no doubt as to the central 

 position of the proteins in the organisation of living matter. 

 Apparently, they occur in nature in close connection with vital 

 processes ; in the living cell they are completely irreplaceable ; 

 and, above all, they alone display the specific properties of 

 living matter. In consequence, the distinctions observed, not 

 only between different kinds of organisms, but even between 

 individuals of the same kind, reappear on chemical investigation 

 as variations in the respective proteins. 



Again, the proteins are capable of showing diversity and fine 

 gradation, both in chemical structure and physical modification, 

 to an extent which is lacking in any other class of substances. 

 On account of the high molecular weight of even the simpler 

 proteins, physical changes are brought about by minute quan- 

 tities of substances of low molecular weight. Electrolytes in 

 particular cause such changes very easily, owing to the 

 amphoteric nature of the proteins. 



The biologist attempts to arrive at a general expression for 

 the profound and diverse phenomena of life, and finds that the 

 rich variety of the reactions of the proteins confronts him as one 

 of his greatest difficulties. Such progress as has been made has 

 occurred mostly in recent years and has been largely due to the 

 application of physical chemistry, and of the youngest branch 



