CATALYSIS AND THE ENZYMES 



the slightest alteration. Finally, as we have al- 

 ready seen, no trace of the catalyser appears in 

 the final products of the reaction. Reactions 

 which show these characteristics we call Catalytic 

 Reactions. The enormous power of the slightest 

 trace of a catalytic substance strongly reminds the 

 biologist of the effects of stimulation in animals 

 and plants. Even here a slight stimulus very often 

 produces a surprisingly great effect. Physiologists 

 know that there is as a rule no mathematical 

 relation between the energy of the stimulus and the 

 energy which becomes manifest in the reaction. 

 For such physiological phenomena the expression 

 Release Action was used. Pfeffer tried to compare 

 such processes with the mechanism of a machine 

 which may be set working by touching an electric 

 button or a spring. Indeed, in both cases the 

 releasing action is not at all comparable with the 

 resulting action. May catalytic effects also be 

 called release actions ? Physiologists sometimes 

 did so, but there is no doubt that there are reasons 

 enough for drawing an exact distinction between 

 the two results. When the trigger of a gun is 

 touched, it does not matter whether more or less 

 power is applied. The energy produced by the 

 explosion is always the same. In catalytic re- 

 actions, on the other hand, the quantity of the 

 catalyser employed is of great importance as 

 regards the amount of the reaction effect. Between 

 certain limits one may even consider the reaction 

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