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?

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?

Questions

Lactose is a disaccharide: It is formed from the combination of glucose and galactose.

This reaction can be reversed by the enzyme lactase.

LactoseLactose

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

Illustration:

milk lactase milk +lactase

milk +boiled lactase

Glucose Test Strip Key:

Light blue-No Glucose

Green to brown-Glucose present

V. Observations/Data Collection

Analysis / Data Presentation

Data tables

Table 1. Color of test strip

Milk Lactase

Milk +

lactase

Milk +

boiled lactase

Starting color

Color at 60 sec

Table 2. Presence or absence of glucose

Milk Lactase

Milk +

lactase

Milk +

boiled lactase

Post-lab questions1. 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?