Effect of Temperature on Enzyme Activity

Investigating the Effect of Temperature on Enzyme Activity Almost all chemical reactions that occur in living organisms are catalyzed by enzymes. Many factors in a cell’s environment affect the action of an enzyme. In this investigation, you will design an experiment to determine the effect of temperature on an enzyme-catalyzed reaction. You will complete an entire lab write-up using the CHS LAB REPORT FORMAT. Fundamental Question How does temperature affect the rate of an enzyme-catalyzed reaction?

Materials •Raw liver•Forceps •Petri dish•Labeling tape and pen •Dropper pipette•Ice bath •0. 1% hydrogen peroxide solution•3 thermometers •Liver puree•Warm-water bath •25-mL graduated cylinder•Clock or watch with second hand •5 50-mL beakers•Paper towels •Filter-paper disks Part A: Observe the Catalase Reaction 1. Put on apron and safety goggles. Use forceps to place a small piece of raw liver in an open petri dish. Use a dropper pipette to put a drop of hydrogen peroxide solution on the liver.

CAUTION: Hydrogen peroxide can be irritating to skin and eyes. If you spill any on yourself or your clothes, wash it off immediately and tell your teacher. Observe what happens. RECORD in notebook. Liver contains the enzyme catalase, which breaks down hydrogen peroxide (H2O2) to water (H2O) and oxygen gas (O2). When hydrogen peroxide is broken down by catalase, bubbles of oxygen gas are released. 2. With your teacher’s guidance, select the proper equipment and technology to measure catalase activity—a filter-paper disk. . To measure the activity of catalase, use a graduated cylinder to place 25 mL of hydrogen peroxide solution in a 50-mL beaker. 4. Use forceps to dip a filter-paper disk in liver puree. Place the filter-paper disk on a paper towel for 4 seconds to remove any excess liquid. 5. Use the forceps to place the filter-paper disk at the bottom of the beaker of hydrogen peroxide solution. Observe the filter-paper disk, and record the number of seconds it takes to float to the top of the liquid.

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RECORD in notebook. Part B: Design an Experiment 1. Use your observation and knowledge to develop a TESTABLE QUESTION and about how temperature will affect the rate at which catalase breaks down hydrogen peroxide. RECORD in notebook : TQ in When…Will format; 2. Write a BACKGROUND section of the lab by doing some research about enzymes. Use part A of this lab, and the information in section 2-4 of the textbook to help you write this.

Be sure to include the Biological significance (why does it matter how enzymes function; why is it essential to rid the cell of H2O2; why is enzyme specificity important to the speed of the reaction), the Content of the class (what is the enzymatic reaction; what are the products, reactants, and enzymes involved in the chemical reaction; what do you expect to happen to the speed of the reaction when temperature is manipulated; what do enzymes do in chemical reactions), and the Link to this lab (how will you test this in lab; what are the mv, rv, and cvs in the lab).

RECORD in notebook in paragraph format. 3. Write a HYPOTHESIS to include your prediction of what will happen in the lab. RECORD in notebook: HYP in IF…THEN…BECAUSE format. 4. Design an experiment to test your hypothesis. Your experimental plan should include PROTOCOL (materials and procedure in pictures) as well as any appropriate controls and replications (repetitions). Be sure to identify all manipulated, responding, and controlled variables in your experimental plan. Include any necessary safety precautions and safety equipment in your plan. . As you plan your investigative procedures, refer to the Lab Tips box on p. 55 of your textbook for information on demonstrating safe practices, making wise choices in the use of materials, and selecting equipment and technology. 6. Construct a DATA table similar to the one below in which to record the results of your experiment. Perform you experiment ONLY after you have obtained your teacher’s approval of your plan. RECORD data in your notebook. Data Table Temperature (oC)Time (seconds)Observations Trial 1Trial2Trial3

Control Temperature: 7. Make a graph of the results of your experiment. Plot temperature on the x-axis and the variable by which you measured catalase activity on the y-axis. RECORD the graph in your notebook under the ANALYSIS section. Explain this graph. 8. Make a graph of class results in the ANALYSIS section. Explain this graph. In addition to your graph, write the rest of the ANALYSIS section of the lab, using the CHS LAB REPORT FORMAT. Include the following in your notebook: Explain what should have happened Identify what should have happened including the relationship between the time it takes the disk to float to the top and the amount of catalase activity; the optimal temperature for the enzyme; the shape change of enzymes when not in homeostasis and how that changes the effectiveness of the enzyme. Explain what actually happened •Summarize data Explain why these results occurred by incorporating background information •Again, use the information from the background section (enzyme structure, enzyme function, homeostasis, temperature, pH, etc) to explain the actual results.

Compare actual to expected results (describe and explain similarities and differences—use numbers) Use simple statistics to explain data •Be sure to use both extremes represented (coldest, hottest, fastest, slowest) and be sure to use averages (group and class) calculate percent change if appropriate State likely human errors and how these affected the data •What did go wrong, what could’ve gone wrong, explain Explain how the experiment could’ve been done differently •Did this lab protocol actually test the testable question? Were the controlled variables actually controlled? •What could’ve been controlled better? •Was the experimental control actually controlled? 9. Write a CONCLUSION for the lab, again referring to the CHS format. RECORD in your notebook and be sure to include the following: •Re-state the hypothesis and indicate whether it was supported or rejected •Did this protocol answer the fundamental question? •What controlled variable(s) could be changed to better answer the fundamental question? (Describe at least two different ones)

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