Effect of Hydrogen Peroxide Concentration on the Activity Rate of Catalase

Enzymes are catalysts that speed up rates of chemical or biological reactions without themselves undergoing any change in concentration i.e. they are not used up in the reaction. In most cases enzymes are specific for the reaction they catalyze, and are 100% efficient under certain optimal conditions of temperature, pressure, and pH. Hydrogen peroxide is a by-product of metabolic reactions that take place in cells. The enzyme, catalase, found the tissues of living organisms, break down this compound into water and oxygen. In this experiment the rate of activity of the enzyme catalase on hydrogen peroxide, will be studied while the concentration of the substrate (H2O2) will be varied.

Research Question

Does the concentration of hydrogen peroxide influence the rate of the activity of the enzyme catalase?

Hypothesis

By decreasing the amount of hydrogen peroxide added to the same quantity of enzymes, a decrease in enzyme activity is expected.

Variables

Dependant Variables

• Volume of bubbles produced as a result of the hydrogen peroxide being broken down

Independent Variables

• Solutions of hydrogen peroxide at different concentrations (10%, 8%, 6%, 4%, 2%, 1%, & 0.5%)

Control Variables

The control variables need to be constant in order to get valid and accurate results. They are:

• Temperature (maintained at room temperature)
• Concentration of catalase (located in liver cubes of volume 1cm3)
• Time (30 seconds)
• pH of the solutions of the trials, which is a bit basic due to the soap

Material

• Solutions of hydrogen peroxide at different concentrations (10%, 8%, 6%, 4%, 2%, 1%, & 0.5%)
• Soap
• Watch
• 10ml graduating cylinder
• Forceps
• 100 ml graduated cylinder
• Pipette
• Distilled water
• Sharp knife
• Fresh piece of Liver

Controlling the variables

Maintaining the temperature constant at room temperature in the graduated cylinders in all 7 trials is crucial since the temperature may be a factor affecting enzyme activity. Therefore each trial should be conducted remotely from any sources of heat that might affect the experiment.

The volume of liver (1cm3) must also remain constant in the graduated cylinders in all 7 trials. This is because the enzyme activity under study is that of catalase which is present in the pieces of liver; therefore the larger the piece of liver, the more enzymes it contains which might affect the rate of enzyme activity thereby changing the experimental conditions in a certain cylinder.

The amount of soap used should be the same in every trial. The soap is used to break down fatty (lipid) liver cell membrane to release catalase into the solution by disrupting the polar interactions that hold the cell membrane together. Hence if more soap is used in one of the trials the concentration of the enzyme would increase and the final results would be invalid. Furthermore, soap renders a medium basic thereby altering the pH. Hence, adding an unequal number of drops of soap in each trial will render each solution having its own pH which could affect the activity of the enzyme and invalidate the results.

Time is a crucial factor since the activity of catalase is directly proportional to time. If one trial is allocated more time before recording the volume of bubbles the enzyme will be able to break down more hydrogen peroxide and the conditions of the trial would be changed.

Procedure

1. Cut 1 cube of liver approximately 1cm x 1cm x 1cm in size
2. Measure 4 ml of 10% hydrogen peroxide using the small graduated cylinder and insert contents into 100ml graduated cylinder
3. Using the pipette insert two drops of detergent into the 100 ml graduated cylinder (same as step 2) and mix the solutions
4. Using forceps place one cube of liver into the graduated cylinder and wait for 30 seconds before recording the volume of foam in the cylinder
5. Repeat steps 1 through 4 using a different hydrogen peroxide solutions in each trial
6. In order to prevent any contamination between different solutions glass cylinder must be washed thoroughly between each trial