INTRODUCTION: 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.
Each of these enzymes is responsible for one particular reaction that occurs in the cell. In this lab, you will study an enzyme that is found in the cells of many living tissues. The name of ...view middle of the document...
2. Using forceps and scissors cut a small piece of liver and add it to the test tube. Push it into the hydrogen peroxide with a stirring rod. Observe the bubbles.
What gas is being released? (consider the equation) ______________________
Throughout this investigation you will estimate the rate of the reaction (how rapidly the solution bubbles) on a scale of 0-5
(0=no reaction, 1=slow, ..... 5= very fast). Assume that the reaction in step 2 proceeded at a rate of "4"
Recall that a reaction that absorbs heat is endothermic; a reaction that gives off heat is exothermic. Now, feel the temperature of the test tube with your hand.
Has it gotten warmer or colder ___________ Is the reaction endothermic or exothermic? ____________________
3. Pour off the liquid into a second test tube. Assuming the reaction is complete. What is this liquid composed of? _______
What do you think would happen if you added more liver to this liquid? __________________________________
Test this and record the reaction rate. Reaction Rate ___________ (1 – 5)
4. Add another 2 ml of hydrogen peroxide to the liver remaining in the first test tube. What is the reaction rate? ________
Is catalase reusable? Explain how you know.
Part B - What Tissues Contain Catalase
You will now test for the presence of catalase in tissues other than liver. Place 2 ml of hydrogen peroxide in each of 3 clean test tubes and then add each of the three test substances to the tubes. As you add each test substance, record the reaction rate (0-5) for each tube.
Substance Rate of Reaction (0-5)
Based on your observations, which tissues contained catalase? _________________________________________
Do some contain more catalase than others? How can you tell? ___________________________________________
water bathPART C - What is the Effect of Temperature on Catalase Activity?
1. Put a piece of liver into the bottom of a clean test tube and cover it with a small amount of water. Place this test tube in a boiling water bath for 5 minutes.
Remove the test tube from the hot water bath, allow it to air cool, then pour out the water. Add 2 ml of hydrogen peroxide.
CAUTION: Use a test-tube holder for hot test tubes.
arrow What is the reaction rate for the boiled liver...