CHEMICAL PHENOMENA IN LIFE 



disintegration of the enzyme. The higher the 

 temperature the more unstable are enzymes. 

 At a temperature of over 60 degrees enzymes are 

 rapidly decomposed, many become immediately 

 inactive when they are heated up to 63 to 65 degrees 

 Celsius. We therefore understand that there 

 probably exists a certain temperature at which 

 the enzyme work is best done, viz. one at which the 

 accelerating effect of the temperature is strong 

 enough to finish the reaction very quickly, and 

 where the enzyme destroying effect of the tem- 

 perature is not so strong as to paralyse the tem- 

 perature effect on the velocity of the reaction. 

 This relation can be shown graphically by two 

 curves. The line AB shows the acceleration of 

 the enzyme reaction by the rising temperature. 

 We take it for granted that this influence is directly 

 proportional to the temperature. The curve CD 

 shows the destruction of the enzyme by the 

 temperature rising. This influence as far as we 

 know is not simply proportional to the temperature. 

 Suppose the quantity of the enzyme at o is 100, 

 and the quantity at 70 degrees is o, we have to 

 draw the curve CD. So we recognise that the 

 optimum of the effect lies between 50 and 60 

 degrees. Only about 55 per cent is active, but 

 the strong acceleration of the reaction velocity 

 neutralises this diminution. At 60 degrees about 

 40 per cent of the enzyme is active. Consequently, 

 this minus is to be subtracted from the ordinate, 

 104 



