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How Temperature Affects Reation Rate of Enzyme Reactions

The graph shows that as temperature is increased, the reaction rate of an enzyme increases. However, the graph shows that their is an optimum temperature where the reaction proceeds at its maximum. Above that optimal temperature, the reaction rate decreases.

What happens can be explained in terms of kinetics, which essentially means molecular motion. All molecules are in motion (except at absolute zero). As the temperature increases, their motion increases too. In the case of enzyme catalyzed reactions, as the speed of enzyme and substrate molecules increases, the chance for collisions so they can form enzyme-substrate complexes increases. Thus as the temperature rises, the reaction rate increases too. Above the optimal temperature however, this does not apply. The reaction rate begins to decrease again because some of the enzyme molecules are now warm enough so that their shape becomes altered (H bonds begin to break, denaturing the enzymes). As the temperature rises above the optimal then, an increasing number of enzymes become denatured. Fewer and fewer enzymes are able to fit with their substrates at the active site. The reaction rate decreases until at some high temperature, all the enzymes are denatured, and reactions cease.

Links for Further Research

Effects of Temperature

Factors Affecting Enzyme Reaction Rates