ANIMAL PROTEINS 



INTRODUCTION 



PROTEINS are organic compounds of natural origin, being 

 found in plants and in animals, though much more plenti- 

 fully in the latter. They are compounds of great complexity 

 of composition, and of very high molecular weight. The 

 constitution of none of them is fully understood, but although 

 , there are a great number of different individual proteids, 

 they present typical resemblances and divergences which 

 serve to differentiate them from other groups of organic 

 bodies, and also from one another. 



Proteins resemble one another in both proximate and 

 ultimate analysis. They contain the usual elements in 

 organic compounds, but in proportions which do not vary 

 over very wide limits. This range of variation is given 

 approximately below : 



Element. Per cent. 



Carbon 49 to 55 



Hydrogen 6*4 to 7*3 



Oxygen 17 to 26 



Nitrogen 13 to 19 



Sulphur 0*3 to 3-0 



The most characteristic feature of the protein group is 

 the amount of nitrogen usually present. This is generally 

 nearer the higher limit, seldom falling below 15 per cent. 

 This range for the nitrogen content is determined largely 

 by the nature of constituent groups which go to form the 

 proteid molecule. Roughly speaking, proteins consist of 

 chains of amido-acids and acid amides with smaller pro- 

 portions of aromatic groups, carbohydrate groups and thio 

 E. I 



