Name ____________________ Period _______
Accelerated Biology
Liver Lab: Pre–Lab Worksheet
Directions: Read the liver lab and answer these questions in complete sentences.
1. What type of macromolecules are enzymes?
Proteins
2. What is the role of an enzyme?
Speed up (catalyze) chemical reactions
3. What is the role of the enzyme catalase in liver?
To speed up the break down of Hydrogen peroxide (H2O2) into H2O and O2
H2O2  H2O and O2
4. Why is catalase vital to a living cell?
Hydrogen peroxide is a poisonous chemical that is continually formed as a byproduct of
reactions in living cells. Cells must either get rid of it or they will die. Catalase allows
cells to break down the H2O2 into H2O and O2 gas more quickly.
5. Why should you wear safety goggles during this experiment?
You will be working with chemicals and be using glassware.
6. List at least two other safety concerns associated with this lab.
The hot water bath is HOT!!! BE CAREFUL when near this!!!
Make sure backpacks are under the desks
7. What should you do at the end of the lab, even though the procedure instructions do not mention it?
CLEAN UP! One for all and all for one!
If even one lab station is not clean, the entire class will lose points!
Don’t be that person!
Liver and potato need to go in the garbage – not down the sinks!
8. On the prelab, complete the data table columns titled “items tested, questions being investigated and
my prediction.”
Procedure
Item Tested
1
Sand
2
potato
3
Small piece
of liver
(don’t throw
away)
4a
4b
Use small
piece of liver
from
procedure 3
Use
hydrogen
peroxide
from
procedure 3
5 liver
Ground up
liver
5 potato
Ground up
potato
6a
Boiled liver
Question being
Investigated
Do all
substances
cause a
reaction?
Will a
reaction
occur when
plant tissue
is added?
Will a
reaction
occur when a
small piece
of liver is
added?
Is the liver
“used up?”
Is the
hydrogen
peroxide
“used up?”
Will changing
the surface
area of the
tissue have
any effect?
Will changing
the surface
area of the
tissue have
any effect?
What
happens to
the reaction
Predicted Rate
Observed Rate
Conclusion
6b
Warm liver
6c
Room
temperature
liver
(see
procedure 3)
6d
Frozen liver
Teacher Demo
MnO2
Teacher Demo
Acid
(dilute HCl)
Teacher Demo
Base
(NaOH)
when liver is
boiled
(100˚C)?
What
happens to
the reaction
when liver is
warm
(37˚C)?
What
happened to
the reaction
when liver
was at room
temperature
(25˚C)?
What
happens to
the reaction
when liver is
frozen
(0˚C)?
Will a
reaction
occur when
chemicals
other than
those from
living things
are added?
Does pH
affect the
rate of the
reaction?
Does pH
affect the
rate of the
reaction?
Accelerated Biology: LIVER LAB
Enzymes in living tissues control almost every chemical reaction that occurs. In this lab activity,
you will examine the action of an enzyme in liver tissue called catalase, or hydrogen peroxidase, on
hydrogen peroxide. This is one example of an enzyme’s action on chemicals.
Hydrogen peroxide is a poisonous chemical that is continually formed as a byproduct of reactions
in living cells. Since it is poisonous, the cells must either get rid of it or change it to something nonpoisonous. If they don’t, then they will die. Catalase allows cells to break down the H2O2 into H2O and O2
gas more quickly.
In this investigation you will use some plant and animal tissues and determine what happens when
hydrogen peroxide is added to them. You will also investigate some conditions that might affect the rate
of enzyme activity.
PRELAB INSTRUCTIONS: Read the Liver Lab. Go to the data sheet for this laboratory and complete
columns titled “Items tested”, “Questions being investigated” and “My prediction.” You must wear
goggles during the experiment!
Procedure: Describe all reactions as: none, slow, moderate, or fast.
1. Do all substances cause a reaction when added to hydrogen peroxide? To determine this, add a pinch
of sand to a small squirt of hydrogen peroxide in a test tube. Rate the reaction.
2. Will a reaction occur when plant tissue is added to hydrogen peroxide? Drop a piece of potato into a
clean test tube. Squirt hydrogen peroxide into the tube. Rate the reaction.
3. Will a reaction occur when a small piece of liver is added to hydrogen peroxide? Use a small squirt of
hydrogen peroxide and a piece of liver about the size of a small pea. Rate the reaction. Save this test
tube; you will use it for #4.
4. The reaction in procedure 2 and 3 occurs for a time and finally stops. Why? Was it completed? Is all
the hydrogen peroxide changed? Or was something in the liver “used up” before all the hydrogen
peroxide could be changed?
a. Is the liver “used up”? Remove the piece of liver from test tube used for #3, and put it in a clean
test tube. Add some fresh hydrogen peroxide to the used liver. What happens?
b. Is the hydrogen peroxide “used up?” As a control, add some fresh liver to the used hydrogen
peroxide from #3 in the other tube. From the new reactions, determine which had originally
changed–the liver, the hydrogen peroxide, or both.
5. Will changing the surface area of the tissue have any effect on the rate of the reaction? Obtain a
mortar and pestle. Grind a piece of liver in the mortar. Scrape out the ground liver and put it into a test
tube. Wash the mortar and pestle. Grind a piece of potato. Scrape out some ground potato and put it
into a second test tube. Add a small squirt of hydrogen peroxide to each test tube and compare the
reactions with those of procedures 2 and 3 above.
6. Does temperature have any effect on the rate of the reaction? In step three you added liver to peroxide
at room temperature (25˚C). Here we will use three other temperatures of liver or peroxide: Boiled
(100˚C), 37˚C, and 0˚C.
a. What happens to the reaction when liver is boiled (100˚C)? Put boiled liver into a test tube. Add a
squirt of hydrogen peroxide to the boiled liver. Rate the reaction.
b. What happens to the reaction when liver is warm (37˚C)? Put a test tube with a squirt of hydrogen
peroxide into the warm water bath for about 3 minutes. Add a piece of liver. Rate the reaction.
c. What happened to the reaction when liver was at room temperature (25˚C)? See step 3.
d. What happens to the reaction when liver is frozen (0˚C)? Put frozen liver into a test tube. Add a
squirt of hydrogen peroxide to the frozen liver. Rate the reaction.
Your teacher will demonstrate the following procedures.
1. Will a reaction occur when chemicals other than those from living things are added to hydrogen
peroxide? Add a pinch of manganese dioxide to about 2 ml of hydrogen peroxide to determine this.
Rate the reaction.
2. Does pH affect the rate of the reaction? Take 1 piece of raw liver and place it into a clean test tube. Do
this to another test tube. Add 2 mL of sodium hydroxide (a base) to one, and 2 mL of dilute
hydrochloric acid to the second. Check the pH of each tube with small pieces of pH paper. Pour 2 mL
of hydrogen peroxide into each tube and record the rates of reaction.
3. What are the products of the reaction? In other words, what is the gas that is given off during the
foaming action, and what is the liquid that remains when the reaction stops?
ANALYSIS: These questions are to be answered on a SEPARATE SHEET and must be TYPED!
1. Make a list of the reaction rates. Organize the list so the materials that produced the fastest reaction
are listed first and the others are in descending order, with the materials that produced the slowest
reaction last. Compare your list with those of other groups.
Item
Warm Liver (37˚C = 98.6˚F)
Ground up Liver
Room Temp Liver (25˚C)
“Used” Liver
pH 13
Potato
Sand
Boiled Liver (100˚C)
Frozen Liver (0˚C)
“Used” Hydrogen Peroxide
pH 2
Reaction Rate
Fastest
Moderate
Slow
No Reaction
2. Look up the word catalyst in a dictionary. Describe what happened in procedure step 3 in relation to
this definition. Does liver tissue contain a catalyst? Explain.
Liver contains the enzyme catalase. Catalase is an enzyme that acts as a catalyst; it
speeds up the break down of Hydrogen peroxide into H2O and O2.
3. Read about enzymes in your book. What is the relationship between a catalyst and an enzyme? Does
liver tissue contain an enzyme? Does potato tissue contain an enzyme? Explain.
All enzymes are catalysts.
BUT . . .
Not all catalysts are enzymes.
Both potato and liver contain the enzyme catalase. When the potato and liver were
added to the Hydrogen peroxide bubbles were visible; evidence that the H2O2 was
breaking down into H20 and O2 gas.
4. Manganese dioxide does not come from a living thing. Is manganese dioxide a catalyst? Is it an
enzyme? Explain.
Manganese dioxide IS a catalyst. It sped up the breakdown of H202  H2O and O2
Manganese dioxide is not an enzyme. Enzymes are a type of protein molecule produced
in living things.
How do you know that MnO2 is not an organic molecule?
5. The reaction for the breakdown of hydrogen peroxide is:
2H2O2  2H2O + O2(gas)
a. Why is an enzyme important to this reaction?
H202 is toxic! It is a waste product of chemical reactions occurring in our body. If it is
not broken down, we will die!
The enzyme catalase breaks down H202 into water and oxygen; two useful molecules!
6. How does pH affect enzymes? Support your answer with your results.
There is an optimum pH that enzymes work best in. If the pH drops too low, or is raised
too high, the enzyme will cease to function.
Catalase works best in a pH of 7. The catalse did NOT work in the acid environment (pH
= 2), but it did work in the basic environment (pH = 13)
The optimum pH for Catalase is 7
7. How does temperature affect enzymes? Support your answer with your results.
There is an optimum temperature that enzymes work best in. If the temperature drops
too low, or is raised too high, the enzyme will cease to function.
Catalase works best at 37˚C (human body temperature!)
Catalase did not work when it was frozen or boiled!
0˚C and 100˚C are outside of the optimum temperature range!
8. Does an enzyme get used up in a reaction? How do you know?
(HINT: Use your results from step 4.)
No. Enzymes are not used up in a reaction. When you took the “used” liver from
procedure 3 and placed it in “fresh” hydrogen peroxide, the reaction still took place.
Enzymes are like a hammer, not a nail. You can use a hammer again and again.
9. How does surface area affect the rate of the reaction?
Greater surface area  faster reaction rate
As surface area increases, a larger area (more enzymes) comes in contact with the
substrate and reacts to it, thus speeding up the reaction.
CONCLUSION
Summarize what you learned in lab and be sure to use the following key words: enzyme, catalyst,
pH, temp, surface area, denature, animal tissue, plant tissue, hydrogen peroxide and catalase (hydrogen
peroxidase). Use specific test results from your lab to support your statements and be sure to underline
each word.