118 ORIGIN AND NATURE OF LIFE 



the formula instead of a long simple chain 

 branches out in a tree-like way. The formula, 

 as has often been insisted upon, is only a 

 visualizing model, but this property occurring 

 in the model, suggests that the di-amino 

 acid, in actual nature, may furnish a device 

 for changing the relationships in space of the 

 huge growing protein molecule and rendering 

 it more stable than if mon-amino acids alone 

 were present. When di-amino acids are 

 present the giant molecule may remain 

 dynamically stable up to a higher level. 



The mon-amino and di-amino acids form 

 the building stones for the construction of the 

 proteins, and the manner of their doing so 

 is exceedingly simple. Each one has a basic 

 portion, and an acid portion. The acid 

 portion of the one has chemical attraction 

 for the basic portion of the other, and they 

 condense or unite just as the two simple 

 sugars have been seen to unite to form a 

 di-sugar, and the di-sugars to unite to form 

 poly-sugars, otherwise called starches, or cellu- 

 loses of the plants and animals. 



If the two letters A and B be used to 

 represent the changeable body part of each 

 amino-acid so uniting, the constant acid group 

 be represented by the letters indicating the 

 elements in it as COOH, and the constant 



