Enzyme Activity Lab
Background Information:
Enzymes are protein catalysts that speed up chemical reactions of the substrates on which they work. They are specific for their reactions, and are said to fit together like a “lock and key”. This lab will examine the activity of a particular enzyme.
Hydrogen peroxide is continuously produced by your cells. If it is not quickly broken down, hydrogen peroxide will kill your cells. Your liver contains the enzyme catalase, which is responsible for breaking down the substrate hydrogen peroxide (H2O2) in the liver to H2O and O2 gas.
catalase
2H2O2 ------à 2H2O + O2
Hydrogen peroxide -à water + oxygen
This enzyme is also present in the cells of beef liver. In this lab, you will observe the action of this enzyme on hydrogen peroxide.
MATERIALS:
1 cm cubes beef liver (5) test tube rack test tube holder
Forceps 6 mL (or 12mL) hydrogen peroxide
Small plate mortar and pestle 1 cm cubes potato (5)
10 mL graduated cylinder spatula
Water hot plate
5 (or 10) test tubes beaker
PROCEDURE:
1. Copy the table from results twice onto lined paper (one for liver, one for potato).
2. Get 5 equal sized pieces of beef liver from your teacher (use forceps to put on your plate).
3. Start a hot water bath – fill the beaker half way with water and place on hot plate. Turn hot plate on high.
4. Pour 2mL of water into a test tube labeled “water and liver”.
5. Using forceps, carefully place one piece of liver in the test tube. Record your observations.
6. Pour 2 mL of hydrogen peroxide into a second test tube labeled “liver and peroxide”. CAUTION – Do not splash hydrogen peroxide onto your skin. If you do get it on your skin, rinse the affected area with running water immediately, and tell the teacher.
7. Using forceps, carefully place one piece of liver in the test tube. Record your observations.
8. When water is heated, place a piece of liver into two test tubes (one each). Place the test tubes into the hot water bath for about 5 minutes (until heated).
9. Using the test tube holders, remove both test tubes from the hot water bath.
10. To one test tube, add 2 mL of water. Record your observations.
11. To the other test tube, add 2mL of hydrogen peroxide. Record your observations.
12. To a test tube labeled “ground liver and peroxide”, pour 2 mL of hydrogen peroxide.
13. Using the mortar and pestle, carefully grind up the final piece of liver.
14. Using the spatula, scrape the ground liver into the last test tube with 2 mL of peroxide. Record your observations.
15. REPEAT WITH THE POTATO.
Results: Data Table
Size and condition of liver / Experimental liquid / Observations1 cm cube beef liver / 2 mL water
1 cm cube beef liver / 2 mL peroxide
1 cm cube beef liver (mashed) / 2 mL peroxide
1 cm cube beef liver (heated) / 2 mL water
1 cm cube beef liver (heated) / 2 mL peroxide
Analysis and Conclusions:
1. What is the purpose of putting the first piece of liver in water? Why is it necessary?
2. Describe the difference you observed between the liver and ground liver when each was placed in the hydrogen peroxide. How can you account for this difference?
3. Do plant cells contain enzymes that break down hydrogen peroxide?
4. How did temperature affect the enzyme?