Enzyme Lab
Name: ______________________ _______________________
Name: ______________________ _______________________
Throughout your body, at any given time, there are millions upon
millions of chemical reactions occurring. Each of these reactions involves
the breaking of covalent bonds in larger molecules or the formation of
bonds between smaller molecules. Most of these reactions involves a
specific protein, called an enzyme. An enzyme is a protein that
lowers the activation energy so that a reaction can occur within
the body. The purpose of this lab is to investigate enzymes and it what
type of conditions, enzymes work best.
Directions:
1. Read over the lab thoroughly.
2. You will be assigned a group and each group will be assigned a station. It is the job of the group
to do the investigation, collect the data, make the appropriate conclusions, answer any questions,
and report their findings to the rest of the class.
3. Each individual will hand in their own lab reports tomorrow.
Introduction:  each group
The liver makes many different enzymes. Some are metabolic, working to convert fructose and other
sugars into glucose or making glucose and proteins into glycogen for storage. Some enzymes convert toxic
compounds like alcohol and nitrates into less toxic compounds or into compounds that can be easily cleared
from the body. Hydrogen peroxide (H2O2) is a product of many of these types of reactions. It is highly
reactive and can easily damage or kill cells if left intact. Cells use the enzyme catalase to break the hydrogen
peroxide into harmless products. In a cell, catalase is contained in a special type of organelle called a
peroxisome.
The reaction you will be testing is the conversion of H2O2 into water and oxygen gas by the enzyme
catalase:
2 H2O2
catalase
2 H2O
+
O2
Review: Draw a molecule of hydrogen peroxide in the space provided (6 points)
Q1. What is the substrate in this reaction? ________________________________________
Q2. What are the products in this reaction? ________________________________________
Because hydrogen peroxide is a by-product of many biochemical reactions, many cells have catalase activity.
The liver, with its detoxifying functions, has higher levels of catalase than most cells. When hydrogen
peroxide is added to ground beef liver, there will be vigorous bubbling.
Q3. What gas is being released in the bubbles? _____________________________________
Control:

for all these experiments, use a number scale from 0 to 5 describe the level of activity, with 0 =
no reaction and 5 = vigorous bubbling.
a. Take two test tubes: label one “+ control” and the other “- control”
b. Measure 1 mL liver puree with the pipette. Insert the pipette into one test tube, and lower the tip as close
to the bottom of the test tube as possible before squeezing the liver puree out. If liver is smeared on the
sides of the tube, the amount available for reaction will not be consistent among your tests.
c. Put 1 mL liver puree in the other tube, using the same method.
d. Into the first test tube put 3 mL of distilled water. Describe results below.
e. Into the other test tube put 3 mL H2O2. Watch the reaction for several seconds, noting the height of the
bubbles travel as well as the speed with which the reaction occurs. Assign this level of bubbling “4.”
These will be the standards by which you compare the other reactions today.
f.
According to the Second Law of Thermodynamics, the amount of energy available to do work
decreases in the course of any process. Often the energy that is unavailable to do work is in the form of
heat.
Q4. Feel the test tube with your hand – did this reaction give off heat? ___________________
g. Describe your results below.
Please note that the picture does not follow the
directions of the lab – it is being used because it
is relevant to the lab. YOU SHOULD FOLLOW
THE WRITTEN DIRECTIONS OF THE LAB!!!
Trial 1: Effect of Temperature on Enzyme Activity
Increased temperature generally increases the effectiveness of enzymes because as the
enzyme and substrate molecules move around more rapidly, the chances of their
colliding and interacting increases. However, as with all proteins, the three-dimensional
structure is in danger when the temperature gets high enough to break weak bonds.
When bonds are broken and the enzyme loses its three-dimensional structure, the
enzyme is denatured: it loses its activity.
Every enzyme has a range of temperatures at which it is the most effective. Most
enzymes in the human body work best at body temperature, about 37 degrees Celsius.
Q5. What is the temperature of the classroom in degrees Celsius? ________
Q6. What is the temperature of the ice bath? __________
Q7. What is the temperature of the hot water bath? ________
a. Grab 4 clean test tubes and four pieces of tape. On the pieces of tape, number 1-4. These numbers will
relate to the following key:
Tube
Tube
Tube
Tube
1:
2:
3:
4:
temperature of ice bath
room temperature of classroom
37 degrees Celsius
temperature of hot water bath
b. Put 1 mL liver puree into the four clean test tubes using the method described in step 2 of the control
experiment, above.
c. Add to the appropriate test tube 3 mL of the H2O2. Make sure the iced H2O2 goes into the iced test tube.
Make sure the room temperature H2O2 goes into the room temperature test tube. Rate the reactions and
record your results below. Remember to compare back to the control (4).
Ice Bath
Room Temp.
37 C
Hot Bath
Reaction rate
(scale 0 to 5)
d. Make a graph of the activity rate versus temperature below.
5
4
Level Of Activity
Scaled 0-5
3
2
1
Iced
Room
37
Heated
Q8.
Is there a temperature at which the catalase activity was the most effective? Was it the
temperature you were expecting? If it was not, how can you explain the results?
Q9.
Why put the tubes of H2O2 (and not just the liver tubes) into the water baths?
Trial 2: Effect of pH on Enzyme Activity
The pH of a solution is a measure of how acidic or basic it is. Pure water with a neutral pH (in which the H+
and OH- concentrations are equal) has a pH value of 7. An acidic solution has a higher concentrations of H+
ions and a lower pH value (<7): a basic solution has a lower concentration of H+ ions and a higher pH value
(>7).
Enzymes usually have a narrow range of pH values at which they work best, just like they have a
certain optimum temperature range. The pH may alter the shape of the enzyme or add or remove hydrogen
ions from the enzyme, changing the way it binds to the substrate.
Q10. At which pH range do you suppose catalase works best?
a. Label three test tubes with tape “Acid”, “Neutral”, and “Base”
b. Carefully put 1 mL liver puree into each tube.
c. Add 2 mL of the appropriate pH solution into each test tube.
Acids and bases can burn your skin and damage your clothing. Handle these solutions with care.
d. Wait about 20 minutes. While you are waiting, do the activity outlined below.
e. Add 3 mL of H2O2 to each tube. Rate the reactions, and record your results below.
Acid
Neutral
Base
Reaction Rate
(scale of 0 to 5)
f. Make a graph of the activity rate versus pH below.
5
Level Of Activity
Scaled 0-5
4
3
2
1
Acid
Neutral
Base
Q11. At what pH does catalase exhibit the greatest activity? ______________________________
Trial 3: Catalase Activity in Different Tissues
a. label three test tubes “liver,” “potato”, and “egg white”
Q12. Which of these do you predict will exhibit catalase activity? _________________________
b. Put 1 mL of each type of tissue into the appropriate test tube.
c. Add 3 mL H2O2 to each tube. Watch for several seconds, rate the reactions, and record your results below.
Liver
Potato
Egg Whites
Reaction rate
(0 to 5)
d. Make a graph of the activity rate versus tissue type below.
5
Level Of Activity
Scaled 0-5
4
3
2
1
Liver
potato
egg whites
Q13. What do your results tell you about the functions of the different types of tissues?
Describe your results for each tissue tested and your explanations for each result.
When you are finished with your lab, you must clean all test tubes
thoroughly, clean your pipettes out, and wipe your station clean.