The Role of Enzymes

Rucker, Jessie B.             Curie Metro High School
                              838-5041
                      

Objectives:

To explore the role of enzymes in chemical reactions.
To determine what kinds of cells contain more catalase than others.

Apparatus and Materials:

Chalk                               Manganese dioxide
Potato                              Boiling water
Raw hamburger                       Graduated cylinder
Raw liver                           scalpel
Boiled liver                        10-mL test tube
Spinach leaf                        Test tube rack
Carrot                              Spot plates
3 percent hydrogen peroxide

Recommended Strategy:

Phenomenological approach
Comparisons, analogies, and summarization

1. Review the following terms: organic compounds, dehydration 
   synthesis, hydrolysis, potential energy, kinetic energy,
   and activation energy.    
   
2. Place two keys on an overhead projector and have the students
   compare them to the structure of enzymes.

3. Using paper models on the overhead projector, demonstrate to the
   students the role of enzymes in hydrolysis and dehydration 
   synthesis.
      
 STUDENTS ARE NOW READY TO BEGIN THE EXPERIMENT.

PART I
    Measure 2 mL of hydrogen peroxide,H2O2, in a graduated cylinder 
    and pour it into a test tube. Add to the test tube enough manganese 
    dioxide, MnO2, to cover the end of a scalpel.

    1. Describe the reaction.
    2. When the reaction ends, add 2 mL more hydrogen peroxide to the 
       test tube. Does the reaction occur again?
    3. When the reaction ends, add a little more manganese dioxide.
       Does the reaction occur again?
    4. Based on your observations, which of the following statements
       is the most probable assumption? Circle the letter of the 
       statement you choose.
       a. The hydrogen peroxide is used up and the manganese dioxide
          remains unchanged.
       b. The manganese dioxide is used up and the hydrogen peroxide
          remains unchanged.
       c. Both the hydrogen peroxide and the manganese dioxide are
          used up.
       d. Neither the hydrogen peroxide nor the manganese dioxide is
          used up.
      
PART II
    Place three small pieces of each: chalk, hamburger, liver, spinach,
    potato, and carrot on a spot plate. Pour enough hydrogen peroxide
    on each food stuff to fill the depression. Be sure to prepare the
    same amount of each food stuff and to keep them separate.
    
    Note the speeds of the reactions. The faster the reaction, the 
    more vigorously the liquid bubbles and the warmer the container
    becomes. Make a data chart, list the items in order from the 
    fastest reacting to the slowest reacting.
   
    5. Which substances contain more of the enzyme, those at the top
       of the list or those at the bottom?
    6. Are the meats near the top or bottom of the list? the plants?
    7. Which, if any, of the items did not produce a reaction? If a
       substance produced no reaction, explain why.

PART III
    Place three small pieces of raw liver and three small pieces of
    boiled liver on your spot plate. Fill each depression with 
    hydrogen peroxide.

    8. Describe what happens.
    9. Based on this test, what assumption can you make about the
       effect of boiling enzymes?

ANALYSIS
  10. What two products does hydrogen peroxide change into when it
      breaks down?
  11. What effect does a catalyst have on this chemical reaction?
  12. What do you think causes the bubbling in this reaction?
  13. What is the function of an enzyme?
  14. What enzyme acts on hydrogen peroxide in living organisms?
  15. Would this enzyme act on chemicals other than hydrogen 
      peroxide? Why or why not?
 
SUMMARY QUESTIONS
   1. Summarize what you have learned about the role of enzymes.
   2. What analogy can be best used to describe the role of
      enzymes?
   3. Write a list of terms that were used to help you to under-
      stand how enzymes operate. Use each term in an appropriate 
      sentence.