ENZYME LAB

BACKGROUND:


2H2O2(aq) -------------------> 2H2O(l) + O2(g) + catalase(aq)


PURPOSE: To study enzymes and conditions affecting their activity.


MATERIALS AND METHODS: Wear safety glasses!

  1. Place 6 clean test tubes in a stand.

  2. Add a small cube of liver and a sprinkle of sand to test tube 1. Using a glass stirring rod, carefully crush the liver.

  3. Add an equal sized cube of liver and sand to test tube 2 but do NOT crush the liver.

  4. Add an equal sized cube of liver and sand to test tube 3 and crush the liver. Put the test tube in a beaker of ice/ice water and set aside.

  5. Add an equal sized cube of liver and sand to test tube 4 and crush the liver. Add 2 mL of hydrochloric acid and set aside.

  6. Add a small amount of manganese dioxide to test tube 5.

  7. Add a sprinkle of sand only to test tube 6.


    8. NEXT: As you perform the tests below, consider how the reactions compare in all tubes and rank them in the table.

  8. Add 2 mL of hydrogen peroxide to test tube 1 and loosely place a rubber stopper on top (caution: it may pop off; wear safety glasses!).
    Observe the reaction for bubbles, gases, temperature changes, etc.

  9. Observe what happens when you insert a glowing (blown out) splint into the top portion of test tube 1.

  10. Repeat step 8 and step 9 for the other test tubes but do test tube 3 and 4 last.

OBSERVATIONS:

Test Tube
(with hydrogen peroxide)
Reactivity
(bubbles, heat, etc.)
(0=low, 5=high)
Oxygen Generation
(glowing splint test)
(0=low, 5=high)
1. liver (crushed)
0   1   2   3   4   5
0   1   2   3   4   5
2. liver (not crushed)
0   1   2   3   4   5
0   1   2   3   4   5
3. liver (crushed and ice)
0   1   2   3   4   5
0   1   2   3   4   5
4. liver (crushed and acid)
0   1   2   3   4   5
0   1   2   3   4   5
5. manganese dioxide
0   1   2   3   4   5
0   1   2   3   4   5
6. sand
0   1   2   3   4   5
0   1   2   3   4   5


QUESTIONS: Answer in full sentences on separate paper.

1.What was the purpose of test tube 6?

2.Compare your results for test tube 1 and 2. Try to explain the difference.

3.Which substance is the inorganic catalyst in the experiment and why was it helpful to see it's reaction in the context of this lab?

4.a) What was the purpose of the glowing splint test?
 b) Which tubes performed best and why?
 
5.a)What was the effect of cooling down the enzyme with ice?
 b)What temperature do enzymes normally operate at in the body?
 c)If catalase enzyme was placed in a test tube and heated to 100OC, what results would you expect from a glowing splint test? Why?

6.a)What was the effect of adding acid to the enzyme?
 b)How would you expect the enzyme pepsin to perform in this part of the experiment? Why?