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ENZYME ACTION
Introduction: Catalysts are substances that speed up chemical reactions. Organic catalysts are called
enzymes. Catalase is an enzyme normally found in many plant and animal tissues. The biological
purpose of catalase is to destroy toxic substances that may be introduced into cells. Also, some cells use
catalase to destroy cellular debris or worn out organelles. In this lab, we will use a catalase solution
from potatoes and determine the effect of temperature and pH on the action of this enzyme. The substrate
of the enzyme will be 3% hydrogen peroxide (H2O2). Catalase works by the following mechanism:
2 H2O2 --------->2 H2O + O2
The development of oxygen gas can be observed by the foam produced in a test tube.
Materials:
Eye protection Metric ruler
Red-skinned potatoes Test tube rack
Scalpel or knife (for cutting and mashing the potato) Marker pen or pencil
H2O2 Test tube clamps
Test tubes acid (HCl)
Hot water bath base (NaOH)
Ice bath Rocks or pebbles
pH paper
CAUTION! HCl and NaOH are strong acids and bases. If you spill these chemicals on your skin,
immediately wash in running water. Wear eye protection at all times. Be careful of hot water and
hot plates.
Pre Lab Questions (Need help? Use pg. 57 in the Modern Biology text)
1. What type of biological molecules are enzymes? (circle one)
a. proteins b. carbohydrates c. lipids d. nucleic acids
2. Describe how an enzyme works and its importance to all living organisms.
3. TRACE the diagram of enzyme action on page 57 of your textbook, below. Label the appropriate
parts of the picture: catalase, H2O2, H2O, and O2
