MECHANISM OF METABOLISM 20$ 



compounds. All these compkx substances are generally made from 

 simple food compounds as amino-acids, carbohydrates and others. 



These synthetic processes of the cell will, like most endothermic 

 processes, take place only if energy is provided. This condition is 

 usually fulfilled in the living cell, due to the fermenting processes 

 going on continuously. There is a strange interaction between 

 anabolism and intra-cellular fermentation proceeding in the pro- 

 toplasm and this linking together of destructive and constructive 

 reaction is the basis of life processes. The life processes decompose 

 certain substances, the energy liberated allows the formation of proto- 

 plasm, which again liberates energy. Thus a continuous formation of 

 protoplasm is secured. 



An explanation of anabolism based upon chemical experiments is 

 not possible at the present time. In the study of intra-cellular destruc- 

 tion it is possible to trace most processes back to enzymic action. 

 There our knowledge ceases because the nature and mode of action 

 of enzymes is imknown. In the study of anabohsm our knowledge 

 has not even progressed so far. The most promising explanation at 

 present is based upon the reversibility of enzymic action. 



Reversibility of Enzymic Action. — Chemical reactions be- 

 tween organic compounds proceed quite rapidly at first, then become 

 slower and slower until the reaction stops entirely. The reaction is 

 not complete at the time it reaches an equilibrium. If the equilib- 

 rium is disturbed by adding more of the reagents, the process will 

 continue. If, however, the products of reaction are added, the reverse 

 process will take place. Reactions between organic compounds can 

 proceed either way, depending upon the relative concentrations of 

 the reacting substances. The standard example is esterification. As- 

 cetic acid plus alcohol gives ester plus water, 



CH3COOH + CHsCH^OH^^CHaCOOCHaCHs + H2O. 



Acetic acid Alcohol Ester 



The process goes to a certain equilibrium and stops. If ester is mixed 

 with water, it gives acid plus alcohol, until the same equilibrium is 

 reached. If acid and alcohol are added to a system in equilibrium, more 

 ester will be formed. If ester is added, more alcohol and acetic acid 

 will be formed. The same is true with enzymes, at least with some 

 enzymes. Maltase will decompose maltose into two molecules of 

 dextrose. In a concentrated solution of dextrose, however, maltase 



