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Name: Enzyme lab Enzymes are Proteins: Watch them react! Enzymes catalyze chemical reactions… they allow chemical reactions to occur at low temperatures and they LOWER the activation energy needed to start a chemical reaction. We don't have to heat ourselves to break down our lunch!! One kind of enzyme is CATALASE. It is found in living tissues (cells). Catalase is made of 4 polypeptide chains, each of more than 500 amino acids! What a protien!! Catalase breaks down hydrogen peroxide (H2O2 ), which is a poisonous by-product of cellular respiration, into water and oxygen. H2O2 is the substrate. 2 H2O2+ catalase --> 2 H2O + O2 Without catalase, the reaction occurs spontaneously, but slowly… I. We will test for the presence of catalase in liver cells, potato cells, and sand (why sand?). a. Place 2 mL of H2O2 in a test tube. notes Page 1 a. Place 2 mL of H2O2 in a test tube. b. Cut a small piece of liver and put into test tube. c. Push liver into H2O2 with stirring rod. d. Observe bubbles i. What gas is being released? ii. Estimate the rate of reaction on a scale from 0-5 (0=no reaction, …, 5=very fast) iii. This reaction is EXOTHERMIC, it gives off heat. Feel the test tube-- how does an exothermic reaction feel? II. We will test the effect of heating the enzyme catalase on its enzyme activity. III. We will test the effects of grinding the substrate (the potato, liver, and sand) to see how that affects the catalase activity. Set up the following test tubes. If it should be heated, place it in the hot water bath- be careful, it's hot! Record the rate of reaction the answer the questions. Test tube 1 Rate of reaction Liver (solid) + H2O2 Room temperature notes Page 2 2 Liver (ground) + H2O2 Room temperature 3 Liver (solid) + H2O2 Heat 4 Potato (solid) + H2O2 Room temperature 5 Potato (ground) + H2O2 Room temperature 6 Potato (solid) + H2O2 Heat 7 Sand + H2O2 Room temperature Answer the following questions: 1. What are the most likely products of the breakdown of hydrogen peroxide? Think of what you observed in the test tube. 2. What caused the reaction when you put liver into tubes #4-6? 3. How do you explain the difference in activity resulting from the whole piece of liver and the ground liver? (Hint: Consider what was done to the liver before it was placed in the test tubes…) 4. Why is test tube #7 necessary? 5. How do you explain the difference in activity resulting from fresh and boiled liver test tubes? 6. What additional information do the results from test tubes #5-7 provide? 7. What type of macromolecule are enzymes? 8. What is a catalyst? 9. Are enzymes changed during a chemical reaction? Do you think we would be able to reuse the enzyme catalase in this experiment? Explain. 10. Enzymes catalyze hydrolysis reactions in which food polymers are broken up into notes Page 3 10. Enzymes catalyze hydrolysis reactions in which food polymers are broken up into monomers. Give an example of a food you ate today. Explain how enzymes and hydrolysis has affected that food. notes Page 4