Download Enzymes are Proteins: Watch them react! Enzymes catalyze

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Enzyme lab
Enzymes are Proteins: Watch them react!
Enzymes catalyze chemical reactions… they
allow chemical reactions to occur at low
temperatures and they LOWER the activation
energy needed to start a chemical reaction.
We don't have to heat ourselves to break
down our lunch!!
One kind of enzyme is CATALASE. It is found in
living tissues (cells). Catalase is made of 4
polypeptide chains, each of more than 500
amino acids! What a protien!!
Catalase breaks down hydrogen peroxide
(H2O2 ), which is a poisonous by-product of
cellular respiration, into water and oxygen.
H2O2 is the substrate.
2 H2O2+ catalase --> 2 H2O + O2
Without catalase, the reaction occurs
spontaneously, but slowly…
I. We will test for the presence of catalase in liver
cells, potato cells, and sand (why sand?).
a. Place 2 mL of H2O2 in a test tube.
notes Page 1
a. Place 2 mL of H2O2 in a test tube.
b. Cut a small piece of liver and put into test
tube.
c. Push liver into H2O2 with stirring rod.
d. Observe bubbles
i. What gas is being released?
ii. Estimate the rate of reaction on a scale
from 0-5 (0=no reaction, …, 5=very fast)
iii. This reaction is EXOTHERMIC, it gives off
heat. Feel the test tube-- how does an
exothermic reaction feel?
II. We will test the effect of heating the enzyme
catalase on its enzyme activity.
III. We will test the effects of grinding the
substrate (the potato, liver, and sand) to see
how that affects the catalase activity.
Set up the following test tubes. If it should be
heated, place it in the hot water bath- be
careful, it's hot! Record the rate of reaction the
answer the questions.
Test tube
1
Rate of
reaction
Liver (solid) + H2O2
Room temperature
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2
Liver (ground) + H2O2
Room temperature
3
Liver (solid) + H2O2
Heat
4
Potato (solid) + H2O2
Room temperature
5
Potato (ground) +
H2O2
Room temperature
6
Potato (solid) + H2O2
Heat
7
Sand + H2O2
Room temperature
Answer the following questions:
1. What are the most likely products of the breakdown of hydrogen peroxide? Think of
what you observed in the test tube.
2. What caused the reaction when you put liver into tubes #4-6?
3. How do you explain the difference in activity resulting from the whole piece of liver and
the ground liver? (Hint: Consider what was done to the liver before it was placed in the
test tubes…)
4. Why is test tube #7 necessary?
5. How do you explain the difference in activity resulting from fresh and boiled liver test
tubes?
6. What additional information do the results from test tubes #5-7 provide?
7. What type of macromolecule are enzymes?
8. What is a catalyst?
9. Are enzymes changed during a chemical reaction? Do you think we would be able to
reuse the enzyme catalase in this experiment? Explain.
10. Enzymes catalyze hydrolysis reactions in which food polymers are broken up into
notes Page 3
10. Enzymes catalyze hydrolysis reactions in which food polymers are broken up into
monomers. Give an example of a food you ate today. Explain how enzymes and
hydrolysis has affected that food.
notes Page 4