Enzymes are simply protein molecules; they are not living organisms. It is therefore wrong to say that they are killed by heating. Enzyme function is dependent on the specific configuration of the enzyme molecule which is mainly maintained by relatively weak bondings such as ionic, hydrophobic and hydrogen bonds. Heating the molecule above the optimal temperature will disrupt these weak bondings, leading to a loss of the natural configuration of the molecule. If the molecule is not subjected to too high a temperature so that the peptide bonds are still intact, this process is reversible. As only the weak bondings...
substrate molecules.

The two different mechanisms are reflected by the shape of the curve showing the effects of temperature on enzyme activity Fig. 1. The slope of the curve left to the optimum temperature has a temperature quotient of about two Q10 = 2; with a rise in temperature within this range, there is a steady increase in the reaction rate due to increased speed of movement of the substrate molecules. On the other hand, with a rise of temperature above the optimum value, enzyme activity drops drastically due to rapid denaturation of the enzyme molecules.