Decomposition of Peroxide Protocols
Experimental Design
*You will create your own procedure for your variable using the protocols below. Record the procedure
you develop on your lab handout. Be sure to design this procedure before you begin experimenting and
adhere to it throughout the lab. Be as consistent as possible on each trial you complete. Your instructor
should discuss with you how and why we are taking measurements in the manner which follows.
Why do we use liver?
Liver solution, just like all living organisms, contain a structure in their single cell called peroxisomes.
Peroxisomes contain an enzyme, generally known as catalase, that decomposes the poisonous hydrogen
peroxide produced by cells into water and oxygen. Cow liver are our source of the enzyme, catalase.
Safety
**Safety goggles should be worn at all times while in lab.
**Chemicals are used in this lab. MSDS sheets are available in the marked location.
General Protocol for the Decomposition of Peroxide
1. Fill your bucket about ½ full of water.
2. Submerge your graduated cylinder so that it fills completely with water. No air bubbles should
be visible in the cylinder.
3. Stand your graduated cylinder up in the bucket of water, making certain it remains full of water.
4. 10 mL of 1.5% Hydrogen Peroxide should be added to the vial.
5. A small amount of liver solution should be measured out to the black line on the plastic
measuring tool. Do NOT add any liver solution to the vial until you are ready to begin the
reaction. The liver solution contains the catalase enzyme which will immediately begin the
reaction.
6. When you are ready to begin the reaction, quickly add the liver solution to the vial, add your
stopper to the vial making a tight seal, and submerge the vial under water.
7. As you carry out the experiment under water, slowly and carefully roll the vial to evenly
distribute both substrate and enzymes.
8. Complete the data chart you were provided. Be sure to watch the time and take appropriate
data readings.
9. Between trials, rinse your vial with water.
10. All chemicals can be disposed of in the sink.
11. Wash your hands with soap and water prior to leaving lab.
Information about variables
To add extreme heat: You will need to use catalase that has been heated to an extreme temperature of
at least 100 oC.
To observe optimum temperature: Your catalase is obtained from liver solution. Liver solution function
best at a temperature of 30 oC, and most enzymes (including catalase) have optimal function at their
host organism’s normal temperature.
To lower the temperature: The catalase should be cooled, almost to freezing temperatures.
To decrease pH: You will either use a buffer or an acidic chemical such as vinegar to lower the pH of liver
solution. You will want to test the pH of your vial, prior to beginning your reaction, using Hydrion paper.
To increase/decrease substrate concentration: Change the amount of substrate appropriately. Record
the amount that you use. If you find that your reaction happens too quickly to measure any data, adjust
your amount slightly and try again.
To increase/decrease enzyme concentration: Change the amount of enzyme appropriately. Record the
amount that you use. If you find that your reaction happens too quickly to measure any data, adjust
your amount slightly and try again.
To test an enzyme from another source (plant/animal): The enzyme, catalase, can be easily sourced from
many living organisms. We commonly use calf or chicken livers for animal sources and turnips or
potatoes for plant sources. You can also use yeast as a fungal source. Be certain that you measure out
these sources using the measuring tool provided.
Other variable changes: If you wish to or are assigned to change a variable not listed, please discuss this
with your instructor and obtain their signature on your procedure before you begin any experiment.