Sample Lab Experiment

Enzyme Lab

Catalase is an enzyme that speeds the breakdown of hydrogen peroxide (H2O2), a poisonous byproduct of metabolism to H2O and O2.  Without catalase, cells would be damaged by the H2O2 they produce.  In this activity, you will use catalase in liver cells to see how various factors affect enzyme activity.

Materials:  liver, sand, water, hydrogen peroxide, manganese dioxide powder (MnO2), test tube rack, test tubes, graduated cylinder, mortar and pestle, boiling water bath, salt-ice bath.

Procedure:

1. Set up a test-tube rack with four test tubes, label 1,2,3,4.  Pour 2mL of H2O2 into each tube.
2. Add a pinch of sand to tube 1 and a pinch of MnO2 powder to tube 2.  Watch for bubbling, which indicates the release of oxygen.  Estimate the reaction rates using this scale:  0=no bubbling; 1=slow (few bubbles); 2=moderate(some bubbles); 3=fast(a lot of bubbles).  Record the rates on the chart below.
3. To see how grinding tissue affects enzyme activity, grind one pea-sized piece of liver in a mortar with a little sand.  Add it to tube 4.  Place a piece of liver in tube 3.  Estimate and record the rates of bubbling.
4. Label four more test tubes, label 5,6,7,8.  Separately grind two pieces of liver, adding one to each tubes 6 and 8.  Add a pinch of MnO2 to tubes 5 and 7.
5. Place tubes 5 and 6 in a boiling water bath for four minutes. Caution:  Exercise care when using the hot water bath.  Place tubes 7 and 8 in freezer or salt-ice bath for four minutes.  Using a test tube holder, remove the tubes and allow them to come to room temperature.
6. Add 2 mL of H2O2 to each tube and record the reaction rates on your chart.

1.  Why did you test sand for its catalytic activity?

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2.  What effect did grinding tissue have on the reaction rate?

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3.  Propose a hypothesis that would explain this effect?

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4.  Using your data, draw a bar graph showing the relative reaction rate for all the substances?