Introduction:
      Enzymes are proteins that are produced by living cells and that act as catalysts in
biochemical reactions.  A catalyst affects the rate of a chemical reaction, with the
result that the cell can carry out complex chemical activities at a relatively low
temperature.
      It is currently thought that the enzyme, E, combines temporarily with its specific
substrate, S, to form a complex, ES.  A result of this temporary union is the
reduction of the energy required to activate the breakdown of the substrate molecule
into P, the products of the reaction.  In summary:
   E + S --->  ES --->  E + P

      Note that the enzyme is not changed in the reaction and can serve to break
down additional substrate molecules.  Each enzyme is specific for a particular
reaction.
      One enzyme, catalase, occurs almost universally in aerobic organisms and
is remarkably constant in structure in all of them.  The exact function of catalase
within cells is not clear.  It probably prevents the accumulation of toxic levels of
hydrogen peroxide (H2O2), but might also take part in some of the many
oxidation reactions going on in all cells. Hydrogen peroxide is formed as a
by-product of chemical reactions in cells.  It is toxic and soon would kill cells
if not immediately removed or broken down.  (Hydrogen peroxide is also used
as an antiseptic.  However, it is not a good antiseptic for open wounds, because
it is quickly broken down by the enzyme catalase, which is present in human cells.)
 
     A major reaction catalyzed by catalase is the following:
   2H₂O₂  ---->   2H₂O  +  O₂
This reaction occurs spontaneously, but not at a very rapid rate.  When catalase
is introduced, it speeds up the reaction considerably.

Procedure:
 Make sure you have goggles on during this entire experiment!
 Caution- The reagents you will use in this lab may be corrosive, poisonous,
and /or irritants, and  they may damage clothing.  Avoid skin and eye contact;
do not ingest.  If contact occurs, flush the area with water for 15 minutes; rinse
mouth with water; call teacher  immediately.

Part A.
      1. Cut a small piece of liver and determine its mass; then place it in a test tube.
      2. Cut a small piece of potato and determine its mass; then place it in a
          second test tube.
      3. Pour 2 ml of  3% hydrogen peroxide into each of the test tubes.
      4. Light a wooden splint with a match, then blow out the flame.  Insert the
          glowing end into the    bubbles in the test tube with the liver. What happens?
      5. Record your observations.

 Part B
     1. Place a piece of each of the following in a separate labeled test tube:
            A. boiled liver    B. fresh liver    C. boiled potato     D. fresh potato
     2. Add 2 ml of 3% hydrogen peroxide into each of the four test tubes.
     3. Record your observations.

 Part C
     1. Place a piece of liver soaked in HC1 in a test tube.
     2. Place a piece of potato soaked in HC1 in a test tube.
     3. Add 2 ml of 3% hydrogen peroxide to each test tube.
     4. Record your results.

Observations:
Part A:
 
 

Part B:
 
 

Part C:
 
 
 

Questions:
1.  Explain what was happening when you mixed hydrogen peroxide with the liver and potato in Part A?
 
 

2. What differences did you observe between the reaction with the liver and the reaction with the potato?
 
 

3. Explain what happened to the glowing wooden splint? Why?
 
 

4. Explain your results from boiling the liver and potato.
 
 

5. What affect does HC1 have on the reaction? Why?
 
 
 

6. Summarize the general conditions necessary for effective enzyme action.  Are these conditions the same for each enzyme?  Why?