The reaction is as follows: 2H2O2 -------------> 2H2O + O2. This reaction is important to cells because hydrogen peroxide (H2O2) is produced as a bypr...
Enzyme Lab Background information What would happen to your cells if they made a poisonous chemical? You might think that they would die. In fact, your cells are always making poisonous chemicals. They do not die because your cells use enzymes to break down these poisonous chemicals into harmless substances. Enzymes are proteins that speed up the rate of reactions that would otherwise happen more slowly. The enzyme is not altered by the reaction. You have hundreds of different enzymes in each of your cells. Liver and other living tissues contain the enzyme catalase. This enzyme breaks down hydrogen peroxide, which is a harmful product created by your cells. If we use tissue containing this enzyme, we can measure the effect of several different factors on the activity of enzymes. Each enzyme is responsible for one particular reaction that occurs in the cell. In this lab, you will study an enzyme called catalase (KAT-uh-LAYSS). Catalase speeds up a reaction which breaks down hydrogen peroxide, a toxic chemical, into two harmless substances – (1) water and (2) oxygen. The reaction is as follows: 2H2O2 -------------> 2H2O + O2 This reaction is important to cells because hydrogen peroxide (H2O2) is produced as a byproduct of many normal cellular reactions. If the cells did not break down the hydrogen peroxide, they would be poisoned and die. In this lab, you will study the catalase found in beef or chicken liver. It might seem strange to use dead cells to study the function of enzymes. This is possible because when a cell dies, the enzymes remain intact and active for several weeks, as long as the tissue is kept refrigerated. MATERIALS: Each lab station should have the following 3 Test tubes 1 Test tube holder 10-ml Graduated cylinder Hydrogen peroxide solution (found in stores)
Forceps (tweezers) Stirring rod Hot and Cold water baths Fresh liver
PART A - Observe Normal Catalase Reaction Test Tube #1 1) Measure 2 ml of the hydrogen peroxide solution using your graduated cylinder 2) Add the peroxide to test tube #1. 3) Obtain a fresh piece of liver. Push it into the hydrogen peroxide with your stirring rod. Observe the bubbles. The bubbles show a chemical reaction is taking place. 4) Throughout this investigation you will estimate the rate of the reaction on a scale of 0-5 (0 = no reaction, 1 = slow, ..... 5 = very fast). Assume that the reaction in test tube #1 proceeded at a rate of "4". Fill in the data table. 5) A reaction that absorbs heat is endothermic. A reaction that gives off heat is exothermic. Feel the temperature of the test tube with your hand. Discuss with your group if it has gotten warmer or colder?
PART B - What is the Effect of Temperature on Catalase Activity? Test tube #2: Hot Water Bath 1) Put a piece of liver into the bottom of test tube #2. 2) Cover it with a small amount of distilled water. 3) Place this test tube in a boiling hot water bath for 5 minutes. 4) After 5 minutes, remove the test tube from the hot water bath and allow it to air cool. CAUTION: Use a test-tube holder when handling the hot test tube. 5) Pour out the water and add 2 ml of hydrogen peroxide. Record the reaction rate (0-5) in the data table.
Test Tube #3: Ice Bath 1) Put a piece of liver into the bottom of test tube #3. 2) Place this test tube into the ice bath for 5 minutes. 3) Add 2 ml of hydrogen peroxide. Record the reaction rate (0-5) in the data table.
PART C - What is the Effect of pH on Catalase Activity? Teacher demonstration: 1) Your teacher will fill three clean test tubes according to the directions below. Treat each tube as follows: a. Test Tube 4: Add 2ml of acidic peroxide (pH 3). b. Test Tube 5: Add 2ml of basic peroxide (pH 10). c. Test Tube 6: Add 2ml of neutral peroxide (pH 7). 2) Put equal quantities of liver into each of the three test tubes and observe the effects of the varying pH. Record your observations in the DATA TABLE.
DATA TABLE Rate of Reaction (0-5)
PART A
Normal Liver (test tube #1)
Boiled Liver (test tube #2) PART B Ice Bath Liver (test tube #3) Basic Solution (pH 10) PART C Acidic Solution Teacher (pH 3) demonstration Neutral Solution (pH 7)
Observations
Analysis and Conclusions Answer the following questions while referring to your data.
Part A 1. From step 3 of part A, which gas is being released when the liver and peroxide come in contact? ________________________________________________________________________________________ 2. When liver and peroxide produced the bubbles, was this reaction endothermic or exothermic? ________________________________________________________________________________________ 3. At the end of part A there was still some liquid at the bottom of the test tube. What is this liquid? ________________________________________________________________________________________ Part B 4. What is the effect of temperature on catalase? (Best writing skills) ________________________________________________________________________________________ ________________________________________________________________________________________ ________________________________________________________________________________________ ________________________________________________________________________________________ 5. What is the optimum (ideal) temperature for catalase? (Best writing skills) ________________________________________________________________________________________ ________________________________________________________________________________________ ________________________________________________________________________________________ ________________________________________________________________________________________ 6. What would happen to chemical reactions inside the human body if your temperature rose or fell too much? (Best writing skills) ________________________________________________________________________________________ ________________________________________________________________________________________ ________________________________________________________________________________________ Part C 7. What is the effect of pH on catalase? (Best writing skills) ________________________________________________________________________________________ ________________________________________________________________________________________ ________________________________________________________________________________________ ________________________________________________________________________________________ ________________________________________________________________________________________ In General: 8. Which part of this experiment is the control group? _________________________________________
