ENZYMES ARE CATALYSTS

Introduction:

Chemical energy is changed to motion energy.  This allows your body to do work.  Some very important chemicals called catalysts control the rate of the chemical reactions that change the chemical energy.  The catalysts do not change.    In this activity you will see the effect of a chemical reaction in a test tube.

Hydrogen peroxide (H₂O₂) is often used for bleaching.  It is also used for cleaning minor wounds.   H₂O₂  is formed as a by-product of chemical reactions in cells.  H₂O₂ is poisonous to the cells.  It must be broken down or removed immediately.  Otherwise, it would destroy the cells.  In the presence of a catalyst, the cells break down H₂O₂ into two harmless substances.

MATERIALS:

Raw  liver                                                                             graduated cylinder

raw potato                                                                          sand

3% H₂O₂                                                                                                                       boiled liver                                                         

manganese dioxide powder                                       ground liver

2 test tubes                                                                        ground potato

Test tube rack

forceps

PROCEDURE:

1.        Use your pencil to label the test tubes A & B.  Place 3 mL of H₂O₂ into each test tube.  Add a pinch of manganese dioxide to test tube A.  Add a pinch of sand to test tube B.  Record your observations.

2.       Clean out both test tubes.  3 mL of H₂O₂ into each test tube.  Add a piece of raw liver to test tube A and a piece of raw potato to test tube B.  .  Record your observations.

3.       Clean out both test tubes.  (DO NOT POUR THE LIVER AND POTATO INTO THE SINK). Add 3 mL of H₂O₂ into each test tube.  Add ground liver to test tube A and ground potato to test tube B.  Record your observations.

4.       Clean out both test tubes.  (DO NOT POUR THE LIVER AND POTATO INTO THE SINK).   Add 3 mL of H₂O₂ into each test tube.  Put a piece of boiled liver into test tube A and a piece of boiled potato into test tube B.  Record your observations.

 

ANALYSIS:

Classify the substances you placed in the test tubes as

Contains catalyst                              contains enzyme                              contains neither

 

CONCLUSION QUESTIONS:

1.       A.  How does grinding change the rate of the reaction?

B.  Which test tubes did you compare to answer A?

C.  Why do you think grinding affects the reaction rate?

 

2.        A.  How does boiling change the rate of the reaction?

 B.  Which test tubes did you compare to answer A?

C.   Why do you think boiling affects the reaction rate?

 

3.        Catalysts are NOT changed in a chemical reaction.

Design an experiment to prove this statement.