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  1. 1. 004-007_CH02 5/16/06 12:48 PM Page 4 Name ____________________________________ Class ______________________ Date _________________ Chapter 2 The Chemistry of Life Design an Experiment 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. Problem How does temperature affect the rate of an enzyme-catalyzed reaction? Materials • raw liver • forceps • petri dish • glass-marking pencil • dropper pipette • ice bath • 1% hydrogen peroxide solution • 3 thermometers • liver puree • warm-water bath • 25-mL graduated cylinder • clock or watch with second hand • five 50-mL beakers • paper towel • filter-paper disks Skills Formulating Hypotheses, Predicting Design Your Experiment © Pearson Education, Inc., publishing as Pearson Prentice Hall. All rights reserved. Part A: Observe the Catalase Reaction 1. Put on your apron, gloves, 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 Dropper pipette immediately and tell your teacher. Observe what Liver happens. Liver contains the enzyme catalase, which breaks down hydrogen peroxide (H2O2) to water Petri dish (H2 O) 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 technol- ogy to measure catalase activity—either a filter-paper disk or an oxygen probe. If using an oxygen probe, see your teacher for instructions. 3. 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. 4 Lab Worksheets
  2. 2. 004-007_CH02 5/16/06 12:48 PM Page 5 Name ____________________________________ Class ______________________ Date _________________ 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. Number of seconds: _________ Part B: Design an Experiment 6. Formulating Hypotheses Use your observation and knowledge to develop a hypothesis. Develop a hypothesis about how temperature will affect the rate at which catalase breaks down hydrogen peroxide. Record your hypothesis. Hypothesis: ______________________________________________________________________ 7. Designing Experiments Design an experiment to test your hypothesis. Your experimental plan should include a prediction of the result based on your hypothesis 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. If more space is needed, use a separate sheet of paper. Prediction of Result: ______________________________________________________________ Experimental Plan: _______________________________________________________________ © Pearson Education, Inc., publishing as Pearson Prentice Hall. All rights reserved. 8. As you plan your investigative procedures, refer to the Lab Tips box on page 55 in your textbook for information on demonstrating safe practices, making wise choices in the use of materials, and selecting equipment and technology. Lab Worksheets 5
  3. 3. 004-007_CH02 5/16/06 12:48 PM Page 6 Name ____________________________________ Class ______________________ Date _________________ 9. Construct a data table similar to the one below in which to record the results of your experiment. Perform your experiment only after you have obtained your teacher’s approval of your plan. Use a separate sheet of paper if you need more room. Data Table Temperature (؇F) Time (secs) Observations 10. 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. With your teacher’s guidance, select the proper equipment and technology to use—either graph paper or a graphing calculator. Analyze and Conclude 1. Inferring How does the time required for a catalase-soaked filter- paper disk to float reflect the amount of catalase activity in the © Pearson Education, Inc., publishing as Pearson Prentice Hall. All rights reserved. solution? 2. Inferring How did temperature affect catalase activity? Was your prediction confirmed? 3. Drawing Conclusions Many mammals, including cattle and pigs, have body temperatures close to 37ЊC. Does your graph indicate that catalase is most active close to that temperature? How might mammals benefit from that relationship? 6 Lab Worksheets
  4. 4. 004-007_CH02 5/16/06 12:48 PM Page 7 Name ____________________________________ Class ______________________ Date _________________ 4. Evaluating Identify and discuss possible sources of error in your procedure. 5. SAFETY Explain how you demonstrated safe practices when using hydrogen peroxide. © Pearson Education, Inc., publishing as Pearson Prentice Hall. All rights reserved. Lab Worksheets 7