Investigating the Effect of Temperature on Enzyme Activity

Introduction:

Thousands of chemical reactions take place in your cells. Almost all of these reactions require molecules called enzymes. Enzymes are protein molecules that speed up chemical reactions without being used up or changed by the reaction. The shape of an enzyme enables it to "fit" with a particular substance called a substrate. A specific enzyme is required for each chemical reaction. Without the help of thousands of different kinds of enzymes, the chemical reactions in your body would happen too slowly for you to survive.

In this investigation you will discover the properties of an enzyme called catalase. Cell synthesize this enzyme to break down hydrogen peroxide to form harmless end products. (Hydrogen peroxide is formed during cellular respiration.

                   H2O2             ________________>         H2O + O2

                      hydrogen peroxide        catalase                   water + oxygen

                   (substrate)          (enzyme)               (products)

Problem: How does temperature affect the rate of an enzyme-substrate reaction?

Hypothesis:

Materials:

10 ml graduated cylinder

Clock with second hand

Pipets, forceps

Thermometer

1% hydrogen peroxide

Ice bath

Small cup

Warm water bath

Paper discs

Liver puree

Procedure:

1. Observe the reaction - Place a drop of liver puree in a petri dish and add a drop of hydrogen peroxide. What happened? What caused the bubbling? Add 10ml of hydrogen peroxide to your cup.

2. Place one paper disc on a clean piece of paper towel and put two drops of the liver puree on it. Allow it to stay on the towel for 4 second to remove any excess liquid.

3. Using the forceps, place this filter-paper disc at the bottom on the cup with hydrogen peroxide. Record the number of seconds it takes to float to the top of the liquid. Why does it rise? Repeat two more times and average the results.

4. Design your experiment to test your hypothesis. Your plan should include a prediction of the result based on your hypothesis, and any appropriate controls and replications. Identify the dependent and independent variable.

5. Once your teacher has approved your plan, construct a data table to record the results.

 

Temperature (oC)

Time for Disc to Rise (seconds)

Trial 1                     Trial 2               Trial 3       Trial 4

         
         
         
         

6. Make a graph of the results. What will you label your X axis? Your Y axis?

Follow-Up and Conclusion:

1. How does the time required for a catalase-soaked, filter-paper disc to float reflect the amount of catalase activity in the solution?

2. What is your conclusion? Was your hypothesis correct?

3. Why does putting hydrogen peroxide on an open cut cause bubbling? Why doesn't it bubble if placed on the skin?

4. What other factors do you think affect the rate of enzyme action? Select on of the factors and briefly describe how you would test your hypothesis.

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