Activity 1: The Effects of Temperature and Inhibitor
on the Enzyme Catalase Extracted from Potato

Major Chemical Concept

Enzymes are proteins that act as catalysts for biochemical reactions. The rate at
which the catalyzed reaction occurs varies with temperature until the temperature
is reached where the protein catalyst is deactivated. Catalysts are also inhibited by
certain substances, including certain metal ions.

Level

This material is appropriate for first year or advanced high school chemistry classes.

Time

40-45 min

Expected Student Background

Students should understand the role of catalysts in a chemical reaction, the nature
of proteins, and protein structure. They must be able to collect data, prepare a graph,
interpret the graph, and make predictions. If students use Procedure B, they should
know how to collect oxygen gas when it is produced in a chemical reaction.

Safety

Read the Safety Considerations in the Student Version. Materials used in these
activities pose few safety problems. Students should not eat the potatoes used in the
activity. Care should be taken with the hydrogen peroxide and copper(II) sulfate
solutions. Wash with water if any gets on the skin.

Materials (For 24 students working in pairs)

Potatoes (red-skinned or Irish potatoes work well; see Advance Preparation)
0.1 M Copper(II) sulfate solution, CuSO₄ (see Advance Preparation)
Fresh 3% hydrogen peroxide, H₂O₂ (from drug or grocery store), 600 mL
60 Graduated cylinders, 50-mL
60 10- x 150-mm test tubes with stoppers
12 Metric rulers
4 Water baths (large beakers may be used)
Clock with second hand.
12 Graduated cylinders, 10-mL
12 Thermometers
4 Hot plates or burners
12 Gas collecting materials (for Procedure B): one-hole stopper (to fit test-tube) with
glass tubing (or plastic tubing) through hole; flexible hose attached to the glass
tube, leading to water trough filled 2/3 with water and water-filled inverted
12 Graduated cylinders, 100-mL

Advance Preparation

0.1 M Copper(II) sulfate solution: Dissolve 2.5 g copper(II) sulfate pentahydrate
(CuSO₄ . 5H₂O) in 100 mL water.
Potato extract. Prepare the pulp and extract as follows: Peel 2-3 Irish potatoes. Cut the
potatoes into pieces and place them in a blender or food processor. Add about 50 mL
water and thoroughly grind the potatoes. Let the mixture stand for a few minutes, and
filter it through cheesecloth to obtain a pulp-free solution. The enzyme catalase is
soluble, so it is in both the pulp and the liquid extract.
Drug store variety hydrogen peroxide is 3%. It must be fresh!

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