Name __________________________________________ Date ________ Hour ______
Lab: Enzymes and the factors that affect their function
INTRODUCTION:
What would happen to your cells if they made a poisonous chemical? You might think
that they would die. If fact, your cells are always making them. They do not die because
your cells use enzymes to break down these poisons into harmless substances. Enzymes
are proteins that speed up the rate of reactions that would otherwise happen more slowly.
Enzymes are not altered by the reaction and can be reused by the body over and over.
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.
Enzymes are made of protein and are biological catalysts- that is, they speed up a
chemical reaction without changing their own molecular make-up. The molecule that the
enzyme acts on is the substrate and the products are the molecules produced by the
reaction.
Under certain conditions, enzymes are denatured. An enzyme is denatured when the
protein molecule looses its three-dimensional shape and cannot function. Some things
that denature an enzyme are high temperatures and extremes of pH.
REACTIONS USING THE ENZYME AMYLASE
The enzyme used in this laboratory will be the digestive enzyme salivary amylase.
Amylase is an enzyme that digests starch into sugar (glucose). “Amyl” comes from the
Greek word for starch. The digestion of starch begins in the mouth (due to amylase) and
continues until stomach acid inhibits the action. It begins again in the small intestine.
To study amylase, we will use an iodine test. Iodine reacts with starch to form a dark
blue color. In most of the procedures in this lab we will use this simple iodine test.
WRITING THE LAB REPORT FOR THIS EXPERIMENT
You will be writing a full lab report for this enzyme experiment. Use the guidelines sheet
that accompanies this lab report. It will walk you through the steps to write a scientific
report. The following sections give you specific information on what I want you to
include in the lab write up.
Title:
Before writing your title, read through the procedure in this lab. Think about what we are
comparing and what we are trying to find out. These questions will help you figure out
the dependent and independent variables.
Identify the:
Dependent variable (what are you measuring in the results?):
Independent variable (what are you testing or comparing?)
The conditions of the experiment (what enzymes are we using to get our answers?)
Now, on a separate sheet of paper, write your title using the guidelines sheet to help you
with wording.
Problem:
Keeping in mind the independent and dependent variables, what is a question you may
ask that would lead you to completing this experiment? In other words, what is the goal
or purpose of the experiment? Use the guidelines sheet to help you with the wording and
record a problem on your lab report. Be sure to have a subheading for this section.
Background:
In paragraph form, discuss the following questions. DO NOT list a bunch of answers to
these in what looks like a paragraph. Write an essay that includes these topics…. Make
your language arts teacher proud!
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What is an enzyme?
What is a substrate?
What does it mean when a protein is denatured?
In the amylase reaction, what is the substrate?
How does amylase digest carbohydrates in the mouth? Include what type of carbs
they digest, what organs make amylase and what the reaction is called/how the
reaction works.
Explain why the use of starch and iodine dye is a good measure to test the
effectiveness of amylase.
Hypothesis:
Write a hypothesis, for the experiment- name all your variables. Read the guidelines to
make sure your hypotheses have a definite or specific prediction of the outcome and that
they are worded as an if-then statement.
Procedure:
You DO NOT need to copy this portion in your lab report. Just follow the instructions
during the experiment.
The Effect of pH on amylase:
1. Label test tube 1 “HCl”.
a. Add 2 mL of starch.
b. Add 10 drops of 0.1m HCl.
c. Add 1 mL of saliva.
d. Test the pH and record it in the data table.
e. Add 2 drops of iodine solution the test tube.
f. After 2 minutes, check the rate of starch digestion and record the color in your
data chart
2. Label test tube 2 “Water”.
a. Add 2 mL of starch.
b. Add 10 drops of water
c. Add 1 mL of saliva.
d. Test the pH and record it in the data table.
e. Add 2 drops of iodine solution the test tube.
f. After 2 minutes, check the rate of starch digestion and record the color in your
data chart
3. Label test tube 3 “NaOH”.
a. Add 2 mL of starch.
b. Add 10 drops of weak NaOH
c. Add 1 mL of saliva.
d. Test the pH and record it in the data table.
e. Add 2 drops of iodine solution the test tube.
f. After 2 minutes, check the rate of starch digestion and record the color in your
data chart
Conclusion:
Write a conclusion based on your results for the experiment and if you accept or reject
your hypothesis. Explain what happened in the experiment that lead you to that
conclusion and use specific data to back up your answer.
Additional discussion to include in your conclusion:
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Refer to your hypothesis and accept or reject it based on your results.
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Explain the relationship between heat and enzyme function.
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What is it called when heat changes the effectiveness of an enzyme?
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If we mimicked the catalase demonstration your teacher did in class but used
amylase we would find no change in the enzyme. In other words, amylase does
not fall apart under hot temperatures. Think about what your body uses amylase
for and make a prediction why this occurs.
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Based on your experimental results, why would amylase cease (stop) working
once it reaches your stomach?
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Did you make any errors or in what ways could this experiment be improved if
performed again?
Make a graph comparing the affects of acids and bases on enzyme activity.