The Effects of pH, Temperature, Substrate Concentration, and Enzyme Concentration on Reaction Rates
Abstract
A class of proteins called enzymes catalyzes almost every chemical reaction in a cell. Enzymes increase the rates of reaction for those reactions, which are already energetically favorable, by lowering the activation energy. Quite often, the rate of an enzymatically catalyzed reaction is 106-1010 times that of an uncatalyzed reaction under similar conditions making it catalyzed reaction very favorable since it will essentially save time.
The purpose of this experiment is to measure the rates of reaction of the enzyme peroxidase with the substrate guaiacol under varying conditions. To examine the effect of temperature on the reaction rate, the pH, substrate concentration, and enzyme concentration are held constant and reactions are carried out at different temperatures. Each enzyme has an optimal set of conditions at which the maximum reaction rate occurs.
By carrying out the four separate experiments, the reaction rate was determined from the linear part of the absorbency versus time curve. The optimum temperature for an enzymatic reaction is 45°C and the optimum pH is 4. The more concentrated the substrate and enzyme buffer is, the fast its reaction rate will be. The buffer with the faster reaction rate is the most favorable.
Introduction
Enzymes are catalytic proteins that change the rate of a chemical reaction without being consumed by the reaction. In this experiment, the enzyme perozidase is used to convert toxic hydrogen peroxide (H2O2) into water and oxygen. Oxygen will react with guaiacol, which turns brown when oxidized. The darker the color of the reaction, the higher the absorbency at 500 nm, indicating more reaction product is being formed. In this experiment, the temperature, pH, substrate concentration, and enzyme concentration was varied to test its effect on the reaction rate.