CHAPTER IX 



THE SPECIFIC ROLE OF AMINO ACIDS IN 

 NUTRITION AND GROWTH 



That the chemical differences in proteins as deter- 

 mined by their amino acid content must be of con- 

 siderable significance in metabolic processes has been 

 understood in a vague way for a long time. As soon 

 as recognition was gained for the view that the prob- 

 lems of nutrition are concerned with other factors 

 than a mere sufficiency of nitrogen or an adequate 

 intake of potential energy the problems of interme- 

 diary metabolism forced themselves upon the atten- 

 tion of physiologists and led to a thorough apprecia- 

 tion of the value in nutrition of factors previously 

 entirely overlooked or considered of little or no 

 moment. 



Reference to the table on p. 22 will bring out clearly 

 the differences that exist between a few of the typical 

 proteins. The most striking variations in amino acids 

 from a quantitative viewpoint are evident. Such 

 differences are undoubtedly of importance from a 

 nutritional standpoint, but of much greater signifi- 

 cance are the qualitative variations. To point out 

 briefly the most evident of these it may be seen that 



