CHAPTER IV 

 ENZYMES 



IT is becoming more and more recognised that enzymes 

 play a predominant part in the life processes of all 

 organisms, large and small. The results of innumerable 

 investigations all go to show that enzymes are concerned 

 in and control the metabolic and respiratory reactions of 

 all living things . The supply of foodstuffs in appropriate 

 form, the supply of energy required for their utilisation, 

 and the synthesis of simple units into the complex com- 

 pounds characteristic of living entities all fall within the 

 province of enzyme action. It is to the action of enzymes 

 that living cells and tissues owe their ability to perform 

 at low temperatures and with the mildest of reagents 

 a vast number of complicated reactions which so 

 far are beyond the powers of the organic chemist 

 with all the resources of the modern laboratory at his 

 disposal. 



In this chapter we shall consider some of the general 

 properties of enzymes before studying the particular 

 effects of certain of them when we come to deal with the 

 respiratory and metabolic activities which they initiate 

 and maintain. 



Such fermentations as the production of alcohol from 

 sugar solution, the production of vinegar from alcohol 

 and the formation of lactic acid from lactose in the sour- 

 ing of milk, and such putrefactive processes as the break- 

 down of plant and animal materials are among the oldest 

 reactions recognised and used by mankind. A long and 



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