8 



ZOOLOGY 



Proteins 



Complexity 

 of proteins 



readily forms the basis of extremely complex and diverse 

 molecules. It is therefore peculiarly fitted to enter 

 into the living substance, and so far as we know, 

 without it no life would be possible. 



5. When we are regarding the materials of the living 

 body from a chemical standpoint, we speak of proteins, 

 and recognize that within the protoplasm of a single 

 cell there are various kinds of proteins. Thus it is 

 not only true that the protoplasm of different animals 

 and plants differs, but that of any one individual, or 

 of any one of its cells, is far from uniform. Different 

 species may indeed have in their make-up many of 

 the same kinds of living materials, the specific difference 

 being due more to the particular combination than 

 anything else. Thus the words composing this sen- 

 tence are all different though they contain various 

 letters in common. 



6. The proteins are broken down by the chemist, 

 so that they lose their original characters, and of 

 course their relation to life activities. The process is 

 similar to that which occurs in the digestion of foods in 

 the body. They do not go to pieces all at once, but 

 are reduced by a regular series of steps to what are 

 known as amino-acids. These amino-acids are of very 

 many kinds. Emil Fischer has endeavored to climb 

 up the stairway, as it were, toward the complexity of 

 the living stuff. It has long been known that many 

 organic compounds could be produced synthetically 

 that is, put together in the chemical laboratory. 

 Fischer was able to go so far as to produce polypep- 

 tids, which are combinations of amino-acids. The- 

 oretically, it might seem merely a matter of time and 

 patience to get the very substance of protoplasm con- 

 structed, but probably the difficulties are insuperable. 



