Chapter 5 



PROTEINS 



Proteins are organic compounds containing nitrogen, which, together 

 with the carbohydrates and the fats, form the principal part of the solids 

 of living matter. The name comes from a Greek word, proteios, mean- 

 ing first. It was originated in 1839 by a Dutch chemist, Mulder, because 

 of his belief in the widespread occurrence and great importance of the 

 proteins. In nutritiori, the proteins are used principally for body-building 

 and maintenance rather than for providing energy. Protein materials 

 are derived from both plant and animal sources, although in the average 

 American diet animal proteins appear to predominate. 



Like the polysaccharides and fats, proteins can be broken down into 

 their unit structures. These units are amino acids, the "building stones" 



Table 5-1 



Economic Importance of some industries based on proteins * 



Value of products 



Industry Wage earners shipped 



1. Leather and its products 383,175 $3,673,849,000 



2. Meat products, including poultry 274,441 8,766,322,000 



3. Wool, felt, and hair products 230,524 2,432,355,000 



4. Furs and their products 37,561 564,660,000 



5. Sea foods (canned) 20,153 226.519,000 



6. Glue and gelatin 5,372 99,260,000 



951,226 $15,762,965,000 



* Compiled from the 1947 Census of Manufactures, Bureau of the Census, 1950, and 

 from the Statistical Abstract of the United States, 1951, published by the Department 

 of Commerce. 



from which the proteins are constructed. In the common proteins there 

 are about twenty different amino acids; many hundred molecules of these 

 amino acids are combined to form the larger aggregates called proteins. 

 Smaller aggregates of the order of 100 units or less are usually classed 

 as peptides. 



Although proteins do not play as large a role in our economic life as 

 carbohydrates, their importance is very great. They are the distinguish- 

 ing constituents of many essential foods (e.g., meats, fish, poultry, eggs, 



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