1. Enzyme Lab Dr. Ippolito BIO121 SUMMER II 2008

2. Materials Test Tubes Sulfuric Acid 3% Hydrogen peroxide Liver homogenate pH 3 buffer pH 7 buffer pH 11 buffer*

3. Goals Understand and quantify enzyme activity Practice the Principles of the scientific method Develop laboratory skills Develop inductive / deductive reasoning skills

4. Revised Data Table please copy this exactly Tube #ConditionsRel. Activity (cm of bubbles) Rx Time (s) NOTES 1Positive Control 2+ Strong Acid 3pH 3 4pH 7 5pH 11 6Temp 45 C 7Temp 4 C 8Temp 100 C 90.1x Substrate

5. Background

6. Catalase: more accurately, hydrogen peroxidase, this enzyme catalyzes the breakdown of hydrogen peroxide to water and molecular oxygen. Because it was the first enzyme truly characterized, it has a historical name that simply means “catalyst” enzyme. Reaction: 2 H 2 O 2  2H 2 O + O 2 (gas) September 2004 Molecule of the MonthMolecule of the Month

7. About Catalase Catalases are some of the most efficient enzymes found in cells. Each catalase molecule can decompose millions of hydrogen peroxide molecules every second. The cow catalase shown here (PDB entry 8cat) and our own catalases use an iron ion to assist in this speedy reaction.8cat The enzyme is composed of four identical subunits, each with its own active site buried deep inside. The iron ion, shown in green, is gripped at the center of a disk-shaped heme group. Catalases, since they must fight against reactive molecules, are also unusually stable enzymes. Notice how the four chains interweave, locking the entire complex into the proper shape.

8. Why the liver? The liver detoxifies dangerous molecules. What is a ‘dangerous’ molecule? –Some are dangerous because they have a lot of free energy. –The liver carefully extracts this energy, like diffusing a bomb. –How? It oxidizes! It removes the high-energy electrons.

9. Why the liver? One of the side-products includes a lot of Hydrogen Peroxide, which while dangerous, is much less dangerous than the toxic molecules the liver processed. The final step in diffusing this energy is to convert hydrogen peroxide into harmless water and oxygen. So the liver has tons and tons of catalase, because it has tons and tons of H202 to deal with.

10. Get into groups and grab your gear!

11. Expectations Next Thursday : Hand in a SINGLE packet that contains: 1. Title Page (title, names, Summer II 2008). Remember to email me % for group members. 2. Answers to questions 1-13 on page 29 of your lab manual 3. Written summary of the 4 experiments One paragraph per experiment is sufficient. WRITE YOUR HYPOTHESES HERE! 4. A brief discussion on your results. Any unexpected results, experimental errors, or simply an overall conclusion can be concluded.