Chapter IIIB 



THE FUNCTIONS OF THE B VITAMINS 

 IN METABOLIC PROCESSES 



In Chapter I B there was presented a brief discussion of the funda- 

 mental reactions common to most organisms. The purpose of the present 

 chapter is to examine in greater detail those processes the chemical steps 

 of which have been fairly well established and which are believed to be 

 generally utilized by many different types of life. There are undoubtedly 

 some reactions included in this discussion which cannot be demonstrated 

 to occur in all organisms, and likewise other reactions omitted which 

 may be universal. The purpose of this chapter would be defeated and 

 our perspective lost if an attempt was made to be encyclopedic with 

 respect to all the metabolic reactions which have been demonstrated or 

 postulated, and to discuss in detail exceptions to the general schemes. 

 The material presented here is intended (1) to indicate the basic patterns 

 which are usually followed by most cells, (2) to elucidate the nature of 

 the chemical reactions involved, and (3) to establish the positions where 

 the B vitamins are essential. 



Organisms show extreme variation in their ability to carry out many 

 reactions. The numerous end products of glucose metabolism which are 

 produced by different organisms illustrate this point well. However, the 

 differences are often one of degree rather than absolute. Although we 

 often think of one or two specific compounds as being the end products 

 of a particular fermentation process, actually many substances are pro- 

 duced. In no fermentation involving intact cells are the principal products 

 formed exclusively. 



Variations in the chemical processes taking place in cells occur (1) 

 when different organisms are compared, (2) when cells from one tissue 

 are compared with those of another tissue in the same organism, (3) when 

 cells at one age are compared with similar cells at a different age, and 

 (4) when cells and tissues from one individual organism are compared 

 with those of another individual of the same species. These variations, 

 taken as a group, are probably more often of a quantitative rather than 

 a qualitative nature. Many organisms and cells probably have the ability 

 to carry out fundamental reactions, such as we are considering, even 

 though such reactions take place slowly and in many cases have not 



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