Labs & Activities › Catalase lab

Enzyme Lab: Catalase in Liver or Potato

Cut a piece of liver or potato, add hydrogen peroxide, and watch it foam. Then change one condition and find out what that does to the enzyme.

• 45–60 minutes
• Groups of 3–4
• Liver or potato
• Biology BIO.1B.2
• Foundations FB.2.6

Question

How do temperature and pH change the activity of catalase?

Background

Cells make hydrogen peroxide (H₂O₂) as a waste product, and it can damage the cell. Catalase is an enzyme, a protein that speeds up a reaction without being used up. Catalase breaks hydrogen peroxide down into water and oxygen:

2 H₂O₂ → 2 H₂O + O₂

The oxygen gas forms bubbles and foam. Hydrogen peroxide is the substrate, and it fits into the enzyme's active site. In the same amount of time, more foam means a faster reaction and a more active enzyme. A change in temperature or pH can change the shape of an enzyme. When the shape changes enough, the substrate no longer fits and the enzyme is denatured.

• enzyme
• substrate
• active site
• catalyst
• denature
• independent variable
• dependent variable
• control

Plan your investigation

Your group chooses one condition to test. Write a hypothesis in the form If …, then …, because … before you start.

Dependent variable (both): height of the foam, in millimeters, after 60 seconds. Keep constant: size of the tissue piece, amount and strength of hydrogen peroxide, container, timing.

Safety

Materials

Procedure

1. Write your question, your variables, and your hypothesis.
2. Prepare the tissue for each condition. Temperature: hold one piece in an ice bath, one in the refrigerator, one at room temperature, and one in boiling water for 3 minutes, then cool it to room temperature. pH: soak one piece in water, one in vinegar, and one in baking soda solution for 5 minutes, then blot it dry.
3. Pour the same amount of hydrogen peroxide (for example 10 mL) into a clean cup for each trial.
4. Drop one piece of tissue into the cup and start the timer. Do not stir.
5. At 60 seconds, measure the height of the foam from the bottom of the cup in millimeters. Record it in the data table.
6. Repeat for every condition. Do three trials of each condition, using a fresh piece and fresh peroxide each time.
7. Clean up as your teacher directs. Peroxide can go down the drain with plenty of water.

Data

Enter your measurements. The table finds the mean (average) and draws the graph for you.

A. Temperature

B. pH

Analysis

1. Name the independent variable, the dependent variable, and two things you kept constant.
2. Which condition gave the fastest reaction? Use your mean foam heights as evidence.
3. Boiled tissue made little or no foam. Explain why, using the words denature and active site.
4. Cold tissue made less foam than room-temperature tissue, but it was not denatured. What slows the reaction in the cold?
5. The foam stopped growing after a while. What was used up?
6. Write a claim-evidence-reasoning answer: what is the best condition for catalase in your data, and why?
7. Design a follow-up test that changes a different variable, such as the amount of liver or the strength of the hydrogen peroxide. What would you predict?