Enzyme Lab
Name: __________________________________
Background information
Date _____________________ Period _________
All living things are made of cells. Cells are little bundles of chemical reactions. They reproduce, they create
energy, and they break molecules down and build them up. All that action going on is made possible by
enzymes. Enzymes are proteins that act as biological catalysts. Like other proteins they are formed by the
dehydration synthesis amino acids that come together in different shapes to do special jobs, like breaking down
starches or fat molecules. The molecules they act on are called substrates. Like other catalysts enzymes speed
up the rate a chemical reaction without undergoing any change themselves.
Look at the diagram below. When an enzyme combines with the substrate it forms a temporary enzymesubstrate complex, where the specific reaction occurs. Then the product separates from the enzyme, and the
unchanged enzyme is recycled to combine with another
substrate molecule. Note that the enzyme is not altered in the
reaction, so a few enzyme molecules can catalyze a great
number of reactions.
Because of the enzyme’s unique shape, the substrate and
enzyme fit together like a lock and key.
An enzyme is inactivated by a change in its 3-dimentional
shape, and its shape is altered by anything that disrupts the
pattern of hydrogen bonding. This is called denaturing. If the
shape changes too much it will no longer function. Some things that can denature an enzyme are high
temperatures, extremes of pH, heavy metals, and alcohol.
Action of Catalase: Did you know your cells produce a poisonous chemical? Most cells produce hydrogen
peroxide (H2O2) as a harmful byproduct of cellular reactions. Hydrogen peroxide can cause serious damage to
cells. Fortunately, cells have an enzyme called catalase that quickly breaks down hydrogen peroxide into water
and oxygen, preventing damage. The equation of this chemical reaction is as follows:
In this lab, you will study the effect of catalase in three different living tissues: apples, potatoes, and liver. You
will also test the effect of temperature and pH on catalase activity.
PreLab Questions:
1. What is a substrate? _____________________________________________________________
2. Enzymes are biological ____________________________________ that ___________________ chemical
reactions.
3. In this lab we will be testing the rate at which catalase can break down the chemical hydrogen peroxide that
cells make. Identify the enzyme, substrate, and products in this reaction.
E:
S:
P:
4. What do we call it when an enzyme loses its shape? __________________________________
List 2 ways this could happen.
1)
2)
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Enzyme Lab Martin, 2014
Materials: test tube, test tube rack, test tube tongs, test tube brush, graduated cylinder, 3% hydrogen peroxide,
glass stirring rod, beef or chicken liver, apple, potato, knife, paper towels, water, hot water bath, vinegar, soap
Safety: Wear goggles at all times! Wash hands at the end of the lab.
PROCEDURE:
**You are responsible for cleaning your group’s lab supplies, lab table, and sink. Liquids may be poured down
the sink, but solids (ex: liver, potato, apple, paper towels) must be thrown away in the trash!!!**
PART A – Observing Normal Catalase Reaction in Three Different Types of Cells
1. Place 2 ml of the 3% hydrogen peroxide solution into a clean test tube. Repeat with the other 2 test tubes.
2. Take a small chunk of apple and put it in test tube 1. Place a small chunk of potato in the second test tube,
and a small piece of liver in the third test tube. You may have to push them in with the stirring rod.
3. Observe and record data as follows: Throughout this investigation you will estimate the rate of the reaction
(based on how rapid and how much bubbles are being created). Use a scale of 0-5 (0=no reaction, 1=little
reaction, ..... 5= very fast reaction & most bubbles). A reaction that absorbs heat is endothermic; a reaction that
gives off heat is exothermic. Feel the temperature of the test tube with your hand. Has it gotten warmer or
colder - Is the reaction endothermic or exothermic? Note these in your data.
4. Pour out the solution in the sink and shake the solid food out into the trash. Use a test tube brush to clean
out your test tubes.
PART B- What is the Effect of Temperature on Catalase Activity?
1. Put a piece of liver into the bottom of a clean test tube and cover it with a small amount of water. Place this
test tube in a boiling water bath for 5 minutes.
2. Remove the test tube from the hot water bath (use the test tube tongs!), allow it to air cool, then pour out
the water. Add 2 ml of hydrogen peroxide. Record the reaction rate (0-5) in the data table.
3. Clean out test tube and wash.
PART C - What is the Effect of pH on Catalase Activity?
1.
2.
3.
4.
5.
Add 2 ml hydrogen peroxide to one test tube.
Use the pH paper to find the pH of vinegar (just put a drop on the pH paper and read the chart).
Add 1 mL of vinegar to the test tube. Then add a fresh piece of liver.
Estimate the reaction rate using the scale established above and record in your data table.
Clean out test tube and wash.
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Enzyme Lab Martin, 2014
DATA TABLE
Rate of
Reaction
(1-5)
Observations & Conclusions (answer section questions)
Apple
PART A Potato
Liver
PART B Liver after heated
pH of vinegar:
Is it an acid or a base?
PART C Liver with Vinegar
Post Lab Questions:
1. When you added the enzyme Catalase to the hydrogen peroxide solution, what gas was being released?
2. Assuming that the reaction had enough time to finish, what should the liquid be that remains in the test tube?
3. Why are enzymes “reusable?”
4. Using your data, which type of tissue contained the most catalase?
5. What did boiling do to catalase?
6. List 3 controls used in this experiment.
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Enzyme Lab Martin, 2014