All living cells produce a small amount of toxic hydrogen peroxide. Fortunately, all cells have the ability to break this down into harmless water and oxygen gas. Cells do this via an enzyme called "catalyst," specifically an enzyme. An enzyme is a biological compound --- almost always a protein --- that lowers the activation energy of a chemical reaction. In this case, the enzyme catalase speeds up the decomposition of hydrogen peroxide into water and oxygen gas, helping cells rid themselves of this poison. Science students can easily measure catalase activity by eye.
- Skill level:
Things you need
- Raw beef liver
- Graduated cylinder
- Small test tubes
- Hydrogen peroxide
- Ruler with millimetres
Purée liver into a liquid. The liver should be so blended that no part of it is visually different than the rest.
Measure out a set amount of liver purée --- usually 1ml, though any consistent amount would work --- with your graduated cylinder. Distribute it into several test tubes. Try to get as little as possible on the sides of the test tubes.
Clean your graduated cylinder thoroughly, then measure out a predetermined amount of hydrogen peroxide.
Add your hydrogen peroxide to a cylinder of puréed liver. The mixture will bubble into a white foam as the enzyme liberates oxygen gas. Measure the height of the white foam with your ruler in millimetres.
Vary the conditions of reaction. Try reducing the temperature by placing the test tube in hot or ice water --- but not getting any water inside the tube. You can also see the effects of altering the pH with vinegar --- which lowers pH --- or baking soda --- which raises it. Measure as before and compare the different conditions. Lastly, you can observe how greater amounts of substrate compare to trials with greater amounts of enzyme.
Tips and warnings
- Enzymes tend to work best at the conditions of the organism they come from. For example, this enzyme will work best at around the body temperature of a cow.
- For students who are uncomfortable working with animal parts, catalase can be purchased as a disc from laboratory supply companies, but it is more costly.
- Do not ingest anything from this lab.
- Wear gloves when handling raw animal products.
- Wear goggles when working with peroxide.
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