Name_________________________________
Per____ Date_____
Enzyme Lab
Purpose
 To examine the function of enzymes in living cells
 To investigate properties of enzymes
 To distinguish between substrate, enzyme, and product in a reaction
 To collect and analyze data on tissue-specific catalase activity
 To collect and analyze data on the effect of temperature on catalase action
Introduction
What would happen to your cells if they made a poisonous chemical? You might think that they would
die. In fact, your cells are always making poisonous chemicals. They do not die because your cells use
enzymes to break down these poisonous chemicals into harmless substances.
Enzymes are proteins that speed up the rate of reactions that would otherwise happen more slowly.
The enzyme is not altered by the reaction. You have hundreds of different enzymes in each of your
cells.
Each of these enzymes is responsible for one particular reaction that occurs in the cell. In this lab, you
will study an enzyme that is found in the cells of many living tissues. The name of the enzyme is
catalase (KAT-uh-LAYSS); it speeds up a reaction which breaks down hydrogen peroxide, a toxic
chemical, into 2 harmless substances--water and oxygen.
Substrate +
2H2O2 +
Enzyme 
catalase 
Product
+ Enzyme
2H2O + O2 + catalase
This reaction is important to cells because hydrogen peroxide (H2O2) is produced as a byproduct of
many normal cellular reactions. If the cells did not break down the hydrogen peroxide, they would be
poisoned and die. In this lab, you will study the catalase found in liver cells, potato cells, and apple
cells. We can use these enzymes to measure the relative influence of varying several different factors
on the activity of enzymes in living tissue. Each enzyme works best at a specific temperature and pH.
Enzyme Properties
1.
2.
3.
4.
5.
6.
7.
8.
All enzymes are proteins
Enzymes speed up, or catalyze, chemical reactions, often by many thousand-fold
Enzymes are required in small amounts.
Many enzymes require assistants, called cofactors. Cofactors may be metal ions such as iron
and zinc, or vitamins.
Enzymes can be reused. They are unchanged by the reaction.
Enzymes are specific. The substrate is the substance that the enzyme works on. Each
substrate is digested by a specific enzyme
Enzymes are affected by pH (acidity) and temperature. The rate of the reaction is dependent
on these two variables. The rate of the reaction is faster with increasing temperature, but also,
the shape of the enzyme molecule is changed at high temperatures which makes it less
efficient as a catalyst. For most enzyme reactions, there is approximately a doubling of the rate
of reaction for every 10ºC rise.
Enzymes exposed to extremes in temperature or pH become denatured (lose their three
dimensional shape and their activity).
Name_________________________________
Per____ Date_____
PART A – OBSERVE A NORMAL CATALASE REACTION
RATE OF REACTION
(0-5)
OBSERVATIONS
NORMAL CATALASE
REACTION
LIVER ADDED TO
USED PEROXIDE
REUSED CATALASE
What is the enzyme we are observing?
What is the substrate?
What are the products?
When liver is added to the USED PEROXIDE, how did it compare to the NORMAL CATALASE
REACTION?
Why do you think the reaction was different?
Is this enzyme reusable? How do you know?
Part B: Investigation of catalase activity in plant and animal tissue
Extract Type
Activity A
RATE OF REACTION
(0-5)
Name_________________________________
Results
Per____ Date_____
Prepare a bar graph of catalase activity. Include labels.
Rate if Reaction (1-5)
Title of Graph _______________________________________________
Apple
Potato
Liver
Analysis (answer questions 1 – 6 below)
1. Did the results of the experiment support your hypothesis? Explain
2. What type of gas is released in the bubbles?
3. Controlled variables are those conditions that are kept constant between experimental groups. The
controlled variables insure that only one experimental variable is tested per experiment. What are 2
controlled variables in this experiment?
Name_________________________________
Per____ Date_____
Part C: The effect of temperature on the activity of catalase
Temperature oC
Rate of Reaction (0-5)
Activity B
Results Prepare a line graph of catalase activity as influenced by temperature.
Rate of Reaction (1-5)
TITLE OF GRAPH __________________________________________
Temperature oC
Analysis (answer questions 1 – 4 below)
1. Explain the results shown in the line graph. Did the results support your hypothesis?
2. What will boiling do to an enzyme?
Name_________________________________
Per____ Date_____
PART D - WHAT IS THE EFFECT OF PH ON CATALASE ACTIVITY
pH
RATE OF REACTION
(0-5)
OBSERVATIONS
ACID
BASE
NEUTRAL
What is the optimum pH (at what pH does the enzyme work best)?
What is the effect of low or high pH on enzyme activity?
What do you think happened to the enzyme at an acidic pH?
Why do you think there is an optimum pH and temperature?
Lab Report:
Write a lab report for this lab activity. A lab report must be written in
third person! Use the questions from the lab and the lab report
instruction handout to guide you.
EXTRA CREDIT if the lab report is typed!
Plagiarism will result in an automatic zero!!!!!!