Liver Enzyme Lab
Purpose: How will enzyme activity be affected by varying temperatures and pH levels?
Background Information about 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 (substrates or reactants), which are
transformed into different molecules (products). 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 protein 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 and different type of
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. As the reaction occurs bubbles will form indicating
that hydrogen peroxide is being broken down 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:
Hydrogen Peroxide
Water
Oxygen
PRELAB Questions: You do not have to write out the questions. But you do have to answer in complete
sentences, restating the question in your answer.
1. What are enzymes responsible for doing within a cell?
2. Complete the following sentence: All enzymes are _______________________ but not all
_____________________ are enzymes.
3. What THREE (3) factors will affect the effectiveness of enzymes? (HINT: Use your notes and/or
the textbook)
4. Write down the equation for today’s lab and do the following: highlight the reactant(s) in the
equation above yellow. Highlight the product(s) in the equation above green.
5. What is our substrate (reactant) in this lab?
6. What is our enzyme in this lab?
7. What are the products in this lab?
8. What indication will we have that the enzyme is working? (HINT: Look at the products, what
would have these together LOOK like?)
Liver Enzyme Lab
MATERIALS:





Well Plate
Pipette
Hydrogen peroxide (H2O2)
Raw calf liver

Boiling water bath (hot place,
water, beaker)
Ice Bath (ice, water, cooler)
HYPOTHESIS:
If the temperature and pH levels of the enzyme are changed from its normal conditions, than it (will have
Choose one
or will not) have an effect on enzyme activity because ___________________________.
PROCEDURE:
1. You will prepare the contents as outlined below for each corresponding well plate:
a. Well plate #1: Liver (raw), & *H2O2
b. Well plate #2: Liver (cooked) & *H2O2
c. Well plate #3: Liver (frozen) & *H2O2
d. Well plate #4: 5 drops of acid solution, Liver (raw) & *H2O2
e. Well plate #5: 5 drops of base solution, Liver (raw) & *H2O2
* VERY IMPORTANT: DO NOT ADD THE H2O2 to well plates until you are running the
experiment for that test.
2. Your data table should have the following format:
Well
Plate
1
Liver (raw), & H2O2
2
Liver (boiled) & H2O2
3
Liver (cooled) & H2O2
4
Acid solution, Liver (raw) &
H2O2
Base solution, Liver (raw) &
H2O2
5
CONTENTS
OBSERVATION
INTERPRETATIONS
3. The size of the piece of liver should be approximately the same and relatively small.
4. Test ONE well plate at a time.
a. Set-up your well plates with the liver pieces
b. Add 5 drops of H2O2 (if indicated)
c. Record your observations, what do you see happen.
d. Interpret what you think has happened to the enzyme.
5. CLEAN UP; CLEAN UP; EVERYBODY, EVERYWHERE!!!! CLEAN UP, CLEAN UP, EVERYBODY DO
YOUR SHARE!!!
Liver Enzyme Lab
Graphing Practice:
The following data tables is information about three different enzymes. A researcher wanted to see how
changing both pH level and temperature would affect the % enzyme activity. Using the following two data
tables create a line graph.
- Plot all three enzymes on the same graph, using a different colored pencil for each enzyme
(HINT: what would I need to include)
- There should be two separate graphs
- Use smooth following lines to connect the points on your graph
- Refer to your NOTES: HOW TO GRAPH to construct your graphs.
Data Table 1: pH Level vs. % Enzyme Activity
pH
Level
1
Enzyme Enzyme Enzyme
A
B
C
0
0
0
Data Table 2: Temperature vs. % Enzyme Activity
Temperature
(degrees
Celsius)
0
Enzyme A
Enzyme B
Enzyme C
5
0
0
5
13
0
0
10
16
10
0
15
38
22
0
20
50
38
0
25
65
54
0
30
89
79
0
35
97
97
5
40
100
100
12
45
3
80
23
2
100
0
0
3
75
0
0
4
50
8
0
5
23
22
0
6
7
70
0
7
0
95
0
8
0
100
0
9
0
97
8
10
0
76
18
11
0
30
35
50
0
20
37
12
0
8
60
55
0
0
58
13
0
0
90
60
0
0
80
14
0
0
0
65
0
0
98
70
0
0
100
75
0
0
90
80
0
0
22
85
0
0
3
90
0
0
0
95
0
0
0
100
0
0
0
Liver Enzyme Lab
Graphing Analysis Questions:
Answer the following questions based on the data table present. Do not write down the question, but
restate the question in your answer.
1. What is the percent activity of enzyme A at pH 3.5?
2. At what temperature do Enzymes B and C and have the same % activity?
3. Which enzyme(s) work best at an acidic environment (pH 1-6) ? At a basic (pH 8+) environment?
At a neutral (pH = 7) environment?
4. At what pH would Enzyme C probably have 100% activity?
5. The average human body has a temperature of 37 degrees Celsius and pH level of 7.4. Based on
this information which of the 3 enzymes would be found within humans? Using the data available
state and support your position.
ANALYSIS: You do not have to write out the question if you make it clear what you are answering.
1.
2.
3.
4.
5.
6.
Why did you include well plate 1 in the experiment? What was the purpose of this trial?
What is the independent variable of the experiment?
What is the dependent variable of the experiment?
What affect did temperature have on catalase activity?
What affect did pH level have on catalase activity?
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.