Our Guiding Question for this
unit
• How do chemical bonds get made and
broken in a cell?
Hydrogen peroxidase
1. H2O2
H20 + O2
2. Hydrogen peroxidase is a cellular poison
(and is broken down by our body in the
liver.)
3. Other cellular material will “stimulate” the
breakdown too (eg. potato)
How do chemical bonds get
made and broken in a cell?
Something present in cells help stimulate the
breakdown of H202
A protein is responsible for stimulating (or
catalyzing) this reaction.
What is a protein?
What makes it work this way?
To help answer this question lets
take a closer look at:
Lactose Intolerance and Lactase
(Why lactase does a body good)
Questions from Reading
1. Explain why lactase is essential for the proper
digestion of milk.
2. Based on what you know about enzymes, do you
think the lactase molecule can be reused? Why
or why not?
3. Based on what you know about enzymes, do you
think lactase can break down other disaccharides
besides lactose? Why or why not?
4. Imagine you are a doctor or pharmacist: How
would you treat a patient who likes to drink milk
but has lactose intolerance?
Questions
a) What does lactase do?
b) How could you measure the activity of
lactase in an experiment?
c) What happens to the activity of an enzyme
after it is boiled?
Lactose is a disaccharide:
It is formed from the
combination of glucose and
galactose.
This reaction can be
reversed by the enzyme
lactase.
Lactose
Lactose
Lactase lab
Pre-lab questions:
• What does lactase do?
• How can the activity of lactase be
measured in an experiment?
• What controls would you need for an
experiment to test the activity of lactase?
Lactase Lab
• We will conduct a lab to
determine how boiling affects
the activity of an enzyme.
Testable question:
How does boiling affect the activity
of an enzyme?
• Materials: 4 test tubes, test tube
rack, milk (lactose), lactase
solution, boiled lactase solution,
4 glucose test strips, pipettes
Lactase Lab
Glucose Test Strip Key:
Illustration:
Light blue-No Glucose
Green to brown-Glucose
present
milk
lactase
milk +
lactase
milk +
boiled lactase
Data tables
V. Observations/Data Collection
Table 1. Color of test strip
Milk
Lactase
Milk +
lactase
Milk +
boiled lactase
Starting color
Color at 60 sec
Analysis / Data Presentation
Table 2. Presence or absence of glucose
Milk
Lactase
Milk +
lactase
Milk +
boiled lactase
Post-lab questions
1. What color on the test strip means that
glucose is present?
2. What color on the test strip means that
glucose is not present?
3. From your results, how do you know that
milk doesn’t have glucose in it?
4. Glucose was present when lactase and
milk were mixed. From your results, how
do you know that the lactase solution didn’t
have glucose in it before it was mixed?