THE LIVER ENZYME LAB
Name: __________________________
Date: ______________________ Per: _________
*-INCLUDE IN LAB WRITE UP
Standard: 1b
Students know how enzymes are proteins that catalyze reactions without altering the reaction equilibrium and the
activities of enzymes depend on the temperature, ionic conditions, and pH of the surroundings.
*Purpose:
To test the effectiveness of enzymes under different temperatures.
Introduction to Enzymes
In each individual cell of a human there are many chemical reactions taking place, performing the necessary
functions for being a large, complex, multicellular organism. This is relatively easy to understand. How do these
reactions occur? This is not so easy to understand. Chemical reactions involve the breaking and reforming of
chemical bonds between molecules (substrate(s) of the reaction), which are transformed into different molecules
(product(s) of the reaction). Chemical reactions can occur spontaneously (without added energy or intervention),
and indeed many of the chemical reactions necessary for life processes are spontaneous; some however, are not.
Metabolic pathways are processes, which involve many chemical reactions that occur in a specific order.
Enzymes are biological catalysts. They help to increase the rate of chemical reactions. Enzymes are most often
proteins and their three-dimensional shape is important to their catalytic activity. Because of their 3-D shape,
enzymes are highly specific for the reactions that they catalyze. In other words, they are highly specific for the
substrates that they will act upon. So any one "function", such as getting energy from a glucose molecule, actually
involves many reactions, each with a specific enzyme.
Enzyme activity is influenced by many factors. You will conduct a series of experiments and observe the reaction
that takes place in several test tubes. The reaction that we will be studying is the decomposition of 6% hydrogen
peroxide into water and oxygen gas. This reaction will be catalyzed by the catalase enzyme found in liver. Catalase
is an enzyme, which is found in many cells, but in highest levels in the liver because the liver often functions to
break down toxins present in the blood.
*Formula for today’s reaction:
*PRELAB #: You do not have to write out the questions.
1. What is an enzyme?
2. What to enzymes do?
3. Define catalyst.
5.
4. Complete the following sentence:
a. All enzymes are
_______________________ but not
all _____________________ are
enzymes.
Do a little research and determine THREE (3) factors that will effect the effectiveness of enzymes: (hint: look in
your book)
a.
b.
c.
6. Highlight the reactant(s) in the equation above yellow. Highlight the product(s) in the equation above green.
7. What is our substrate in this lab?
8. What is our enzyme in this lab?
9. What indication will we have that the enzyme is working? HINT: Look at the products, what would having these together LOOK like?
MATERIALS:
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5 test tubes
1 test tube rack
Hydrogen peroxide (H2O2)
Distilled water (d H2O)
Raw calf liver
Boiling water bath (hot place, water, beaker)
Ice Bath (ice, water, cooler)
PROCEDURE:
1. You will prepare the contents as outlined below for each corresponding test tube:
a. Test tube #1 – Water
b. Test tube #2 – Water & Liver
c. Test tube #3 – Water, Liver, & *H2O2
d. Test tube #4 – Water, Liver (that has been boiled several minutes) & *H2O2
e. Test tube #5 – Water, Liver (that has been cooled on ice for several minutes) & *H2O2
* VERY IMPORTANT: DO NOT ADD THE H2O2 to tubes #3-5 until you are running the experiment for that test tube.
2. * Your data table should have the following format:
TEST TUBE #
CONTENTS
HYPOTHESIS
1
OBSERVATION
INTERPRETATIONS
2
3
4
5
3.
4.
5.
6.
7.
Record a hypothesis for EACH test tube set-up BEFORE beginning the lab.
The volume of water will always be 5mL
The size of the piece of liver should be approximately the same and relatively small.
Place test tubes 4 & 5 in ice/water bath as soon as you prepare it.
Test ONE test tube at a time.
a. Set-up your test tube
b. Add 5mL of H2O2 (if indicated)
c. Record your observations for ~3 minutes.
d. Interpret what you think has happened to the enzyme.
8. CLEAN UP; CLEAN UP; EVERYBODY, EVERYWHERE!!!! CLEAN UP, CLEAN UP, EVERYBODY DO YOUR
SHARE!!!
*ANALYSIS: You do not have to write out the question if you make it clear what you are answering.
1. What effect did the water have on enzyme function?
a. How do you know?
2. What effect did the ice have on enzyme function?
a. How do you know?
3. What effect did the heat have on enzyme function?
a. How do you know?
b. Explain why you think this happened?
4. Why did you include test tube 1 in the experiment?
5. Why is it important to maintain the same volume of water and H2O2?
6. What is the independent variable?
7. What is the dependent variable?
8. Explain how enzyme function is like a lock and key. (You may draw and label a diagram in addition to writing an
explanation if that makes it easier for you.)
9. The function of the liver is to break down fats and build certain proteins. Cirrhosis of the liver is a disease which
causes the liver to become thickened and “rubbery.” Hypothesize how enzyme function in the liver would be
affected in a person with cirrhosis.