Enzyme/Catalase Reactions Lab Name _______________________ Date________ Block_____ Background 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. Enzymes are proteins that function as biological catalysts. Catalysts are substances that speed up chemical reactions. Catalysts are NEVER used up. They are typically identified by the ending “ase”. Enzymes either: 1. Catalyze the breakdown of a substrate molecule into products. 2. Catalyze the assembly of substrate molecules (monomers) into a larger product (polymer) This lab will use the enzyme catalase and the substrate hydrogen peroxide. The reaction: 2H2O2 + catalase à 2H2O + O2 + heat + catalase Notice that catalase is not changed by the reaction, and that the reaction produces heat. Hydrogen peroxide will break down all by itself (spontaneously) at a slow rate. Catalase makes the reaction thousands of times faster and causes bubbling. We will measure the reaction rate “rating” the amount of bubbles being produced. Enzyme-Substrate Complex All enzymes are proteins with active sites that have a shape that must exactly fit the substrate. Heat and strong acids/bases can destroy the shape of the active site and make the enzyme not able to do its job. This is called denaturation.

PRE-LAB: Use your Section 2.4 notes and the background information above.

1. Waste can build up in our cells over a period of time. Why don’t they die?

2. Identify the reactants and products of the chemical reaction in the background information of this lab.

3. Why is the enzyme “catalase” still present on the right side of this chemical equation?

4. The name of an enzyme often ends in ______________________.

5. Explain HOW an enzyme functions. (include the words, substrates, products, active site, and enzyme-substrate complex)

6. What will happen to the cell if the enzyme to break down a toxic substance has been denatured? Explain.

7. In your notes we discussed 3 possible things that could “denature” an enzyme. What are these?

Where is Catalase Found? Hypothesis: If ___________________ is present, then the reaction will _______________________, because

___________________________________________________________________________________________________________

Manipulated Variable= _____________________ Responding Variable = _________________________ Materials: potato, carrot, liver, chicken, distilled water, test tubes, graduated cylinder, H2O2.

Procedure: 1. Label your test tubes 1-6.

2. Using the graduated cylinder, add 3ml of distilled water to test tube #2. Now, using the graduated cylinder, add 3ml of Hydrogen Peroxide (H2O2) to test tube #1 (control). 3. Carefully place a small quantity of each material listed below in the appropriate test tube. (See Table)

4. Do not cross contaminate material. 5. Now, add 2 ml of H2O2. to each test tube using the graduated cylinder and record observations by ranking it on a scale from 0-5. (0 = no bubbling, while 5 = extreme bubbling - foaming coming out of the tube)

Analysis After looking at the data collected, what can you conclude about where catalase is found?

Part II: What Effect Does Temperature (Heat) Have on Enzyme Function?

Hypothesis: If catalase is ______________, then the amount of oxygen bubbles will ____________________, because __________________________________________________________________________________________________________ Manipulated variable = ___________________________ Responding Variable = ______________________________ Materials: raw liver, cooked liver, 2 test tubes, graduated cylinder, H2O2

Procedure: 1. Carefully place a small pea sized piece of raw liver in one test tube, and one piece of “cooked” liver in the other.

2. Add 2 mL of H2O2 to each test tube using the graduated cylinder and observe, still using the 0-5 rating scale used earlier.

Group Reaction rate (0-5) Control (raw) Experimental (cooked)

Tube #1 Tube #2 Tube #3 Tube #4 Tube #5 Tube #6 Substance H2O2 only

(control) Distilled Water

Potato Carrot Liver Chicken

Reaction rate (0-5)

Conclusion for Part II: (Do your results cause you to accept or reject your hypothesis? Use your data to support your answer.) ____________________________________________________________________________________________________________

____________________________________________________________________________________________________________

____________________________________________________________________________________________________________

____________________________________________________________________________________________________________

Part III: Does pH (acid) destroy an enzyme’s ability to speed up a chemical reaction?

Hypothesis: If ______________ is added to catalase, then ________________ (less/more) bubbles of O2 will be produced. Manipulated Variable = ___________________________ Responding Variable = ______________________________ Materials: dropper, liver extract, 2 test tubes, water, graduated cylinder, H2O2

Procedure: 1. Carefully place 20 drops of liver extract in each of two test tubes. 2. Add 3mL of HCl (two squirts) to one tube (experimental). 3. Add 3 mL of water (two squirts) to the other test tube (control). 4. Swirl both test tubes for 3 minutes. 5. Add 5 mL of hydrogen peroxide to each test tube using the graduated cylinder. 5. Record your observations, still using the 0-5 rating scale used earlier. Group Reaction rate (0-5) Control (water) Experimental (HCl) Conclusion for Part III: (Do your results cause you to accept or reject hypothesis? Use your data to support your answer.) ____________________________________________________________________________________________________________

____________________________________________________________________________________________________________

____________________________________________________________________________________________________________

____________________________________________________________________________________________________________

Part IV: Questions 1. Draw a diagram that shows the enzyme/substrate complex for catalase, H2O2, water, and O2. LABEL each part. (Use Section 2.4 in your textbook and the background information in this lab for help) 2. What is the function of catalase in living cells? 4. What happens to an enzyme's ability to catalyze a reaction when they are heated? How does your data show this? 5. Describe what happens to the active site of enzymes when they are exposed to high temperatures or strong acids. 6. What effect does HCl (acid) have on the catalase enzyme? 7. What is the substrate catalase bonds with? ______________________________ 8. What is hydrogen peroxide changed into when catalase reacts with it? 9. Is catalase changed during the reaction? (BE CAREFUL!!!) 10. Some enzymes are said to be “denatured” if exposed to extreme heat, cold, acidic, or basic conditions. What does this mean and how is this being shown in this lab 11. EXPLAIN why an enzyme is a catalyst, but a catalyst isn’t necessarily an enzyme.