Biology Enzyme Lab- Experimental Design
Introduction:
If you have problems digesting milk, ice cream, yogurt,
cheese or other dairy foods, chances are that you are one of
the 75% of the world’s population who are “lactose
intolerant”. Lactaid is a product designed to help people who
cannot digest milk sugar (Lactose) because they are missing
the enzyme Lactase. Normally, in our digestive system,
Lactase is the enzyme that breaks down lactose into two
monosaccharides: glucose and galactose so that our body can use the glucose as energy.
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To test for the presence of monosaccharides (such as glucose) and reducing disaccharide sugars
in food, the food sample is dissolved in water, and a small amount of Benedict's Solution is
added.
Benedict’s Solution: The solution should
progress from blue (with no glucose
present), to green, yellow, orange, red, and
then brick red when there is a large amount
of glucose present.
Background Information:
Lactose intolerance is usually caused by a lack of lactase. When the body does not have enough
lactase enzyme, the undigested lactose sugar is moved into the colon, where it becomes
fermented by intestinal bacteria. The fermentation process produces a lot of gas and causes the
unpleasant discomfort of bloating, cramps, and diarrhea. The amount of reaction and discomfort
differs among individuals. Some people have mild symptoms that pass quickly, while others can
have severe symptoms that leave them feeling ill for many hours.
Interestingly, most people are born with the ability to produce the lactase enzyme and can digest
lactose sugar during infancy and early childhood, while drinking mother’s milk. But many
lactose intolerant people gradually produce less lactase as they grow older.
If you have lactose intolerance, you should know about “hidden” sources of lactose. Although
milk and foods made from milk are the only natural sources of lactose sugar, lactose is often
added to prepared foods. Some so-called “non-dairy” products (powdered coffee creamer and
whipped toppings) may include ingredients that come from milk, and therefore contain lactose.
Lactose is an added ingredient in more than 20% of prescription drugs and about 6% of over-thecounter medicines.
Many people who are lactose intolerant avoid dairy foods and foods containing lactose.
However, these foods generally do not have to be eliminated from the diet. To make foods
containing lactose easier to digest, natural enzyme supplements can be taken before or with a
meal. Supplements such as Lactaid can help make lactose-containing foods easier to digest.
Lactaid contains the enzyme lactase. The caplet form of Lactaid is swallowed or chewed
before eating dairy products. The drop form of Lactaid is mixed with milk to produce lactosefree milk. When you use any of these supplements, you are eating the enzyme that you normally
would be producing.
Pre-Lab Questions
1. What is the sugar found in milk?
2. What enzyme breaks down the milk sugar?
3. What are the two simple sugars that make up milk?
4. If you are lactose intolerant, explain how your body will respond to the milk sugar.
5. What is Lactaid? How can it be beneficial to someone who is lactose intolerant?
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Procedures: In this lab, you will investigate the action of the enzyme lactase. Specifically, you
will be designing a detailed experiment to test the effect of Lactaid on milk. The directions
below will guide you in planning the experiment so that you test all possible variables. The goal
is to understand how Lactaid functions to help people with lactose intolerance and also to
understand how enzymes function in general.
Design an experiment where you would determine how quickly Lactaid works to break down
milk sugar in different conditions.
Experimental Control: Complete the tests below to see positive and negative results
Beaker
Positive Control Test
Sugar Water
Negative Control Test
Tap Water
Benedict’s Solution*
* Don’t forget that Benedict’s Solution needs 1-2 minutes in a hot water bath to see results
Why do we need to perform a positive and a negative control test?
The positive control is an experiment whose result is already known to be positive, it is used to
check that nothing went wrong during the procedure.
The negative control is an experiment done with a sample/mock sample that should normally
yield a negative result.
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Materials:
You will be given the following materials:
Benedict’s Solution
Hot Plate
Light Acid
Test Tubes/Rack
Lactaid Pill(s)
Graduated Cylinder
Whole Milk
Timer
Pipettes
Procedures:
Design a controlled experiment that shows the effect of Lactaid on Milk Sugar (Lactose).
Make sure your experiment description includes the following:
Hypothesis: Remember hypotheses are written as “If…then” statements.
Detailed Procedures, which will include:
The effect of Lactaid on Milk Sugar (Lactose)
A test to determine how milk behaves without Lactaid
A test to determine what happens to Lactaid when it has been denatured (temperature and pH)
A data table
EXPERIMENT RESEARCH PROPOSAL FORM
Teacher Approval ________________
1. Title: The Effect of
on
2. Background Information: What do you know about Lactose, Lactase, Enzymes
3. Hypothesis (It must be written in an “If, then” form)
3. Independent Variable (What am “I” (the scientist) going to be testing in this experiment?, “If”)
What treatment will the experimental group receive?
What treatment will the control group receive?
4. Dependent Variable (What data will you be collecting?, “Then”)
5. What factors must be kept constant in each group?
6. Based on Steps 3-5, set up an Experimental Design (Procedure) Use as many steps as
necessary.
a.
b.
c.
d.
e.
7. Data Table (Using a ruler, create a table to collect your data in.)
Title of Data Table: The Effect of
on
8. Complete the experiment. Collect the data in your Data Table.
Write a conclusion in COMPLETE SENTENCES. Be sure to answer all questions below:
€ Restate your hypothesis
€ Was your hypothesis correct or incorrect? Explain your reasoning.
€ Describe one way that you could improve your experiment.
€ Explain one reason for experimental error.
Refer to the equation below and the background information to answer the following questions:
Lactaid (Lactase)
Lactose (Milk Sugar)
Glucose +
Galactose
a. Which molecule(s) is the enzyme in this experiment?
b. Which molecule(s) is the substrate in this experiment?
c. Which molecule(s) is the product in this experiment?
d. What type of organic molecule is lactose?
e. What type of organic molecule is lactase?
3. Is the reaction of Lactaid and lactose sugar synthesis or digestion? Explain.
4. Can an enzyme be used to speed up any reaction or is it specific to just one reaction?
Explain.
5. Explain why enzymes are so important to living organisms. (What is the function of
enzymes?)
In the following diagram, draw arrows to show the sequence of events and label: lactase
(Lactaid), lactose, glucose, galactose. Use the diagram on page 1 to assist you.
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