Factors Affecting Enzyme Activity


            Hydrogen peroxide (H2O2) is a poisonous byproduct of metabolism that can damage cells if it is not removed. Catalase is an enzyme that speeds up the breakdown of hydrogen peroxide into water (H2O) and oxygen gas (O2).

            2H2O2 ➝ 2H2O + O2

Remember that a catalyst is a substance that lowers the activation energy required for a chemical reaction, and therefore increases the rate of the reaction without being used up in the process. Catalase is an enzyme, a biological catalyst, for which hydrogen peroxide is the substrate.

            The assay system used in this investigation consists of a small filter paper disc which is coated with the enzyme and then placed at the bottom of a beaker of substrate (hydrogen peroxide). As catalase breaks down the hydrogen peroxide into water and oxygen gas, the bubbles of oxygen collect on the filter paper disk and make it rise to the surface of the hydrogen peroxide. The time it takes for the filter to rise is an indication of the rate of enzyme activity.

            Rate of enzyme activity = distance (depth of hydrogen peroxide in mm)/time (in sec). We will assume that each filter paper disk is coated with the same amount of catalase.

            We will use a solution of baker’s yeast as a source of the enzyme. Let’s imagine that the solution has is arbitrarily set at 100 enzyme units/ml (a made up unit).

Your job

Write a hypothesis about a factor you think will affect the rate of an enzyme catalyzed reaction and then design an experiment to test your hypothesis. Once your protocol is approved, we will go to the lab to so you can conduct your experiment.