Chapter 



7 



Metabolic Pathways 



By WAYNE W. UMBREIT 



The body of knowledge recalled by the 

 words "metabolic pathway" is an important part of micro- 

 biology. It is perhaps the most intellectual of the fields of 

 microbiology, possibly the least practical; let us hope that 

 it is not the most obscure. 



In the living cell there are varied processes, some of 

 which are dependent upon physical and spatial forces, on 

 tensions, and in a molecular sense, on springs and coils; 

 but the vast majority of living processes are chemical 

 processes, and the living cell, particularly the bacterial 

 cell, is a chemical machine — a chemical mechanism. 



The individual reactions that constitute the chemical 

 processes of living tissues, be they human or microbial, 

 have been intensively studied, and a good deal is known 

 about them. No one would assume, however, that with 

 our present knowledge we are capable of describing all of 

 the varied chemistry of the living process. Further, of 

 those reactions whose course is known, the detailed mech- 

 anism may be considerably different from what we now 

 suppose. I do not propose to outline detailed reaction 

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