SBI3C Virtual Lab
Name: ___________________________
Date: ___________________________
Enzyme-Controlled Reactions
Communication
Thinking & Investigation
/10
/12
TOTAL MARK
/22
(wt-3)
Background Information:
Millions of people suffer from an enzyme related condition called lactose intolerance. Lactose is a disaccharide that is commonly
referred to as a dairy sugar. In normal individuals who eat lactose, their digestive system produces the enzyme lactase which breaks
down the sugar into two monosaccharides – glucose and galactose which can be used by the body. Label the following picture with
the terms: lactose, lactase, glucose, and galactose.
In a person with lactose intolerance, there is not enough of the lactase enzyme produced to break down the substrate lactose. When
this individual eats lactose, it cannot be broken down sufficiently in their digestive tract. This leads to discomfort associated with
lactose intolerance such as cramps, bloating, gas, and diarrhea.
Please visit http://www.mhhe.com/biosci/genbio/virtual_labs/BL_11/BL_11.html to begin the virtual lab.
Purpose:
In this investigation you will determine the effects of substrate concentration and pH on the rate of an
enzyme-catalyzed reaction.
Questions:
1. What is the effect of lactose (substrate) concentration on the rate of enzyme activity?
2. What is the effect of pH on the rate of enzyme activity?
Hypothesis:
1. ___________________________________________________________________________________
2. ___________________________________________________________________________________
Part 1: Effect of lactose concentration on enzyme activity
Procedure:
1. To conduct a controlled experiment, you must determine:
Independent variable: ______________________________
Dependent variable:
______________________________
Controls:
pH and temperature remain constant
An independent variable is
purposefully and steadily
changed to determine its
effect on a second,
dependent variable.
All other variables are kept
constant.
2. In each of the 5 test tubes, a lactase solution (the enzyme) is
already added.
3. Click and drag to add a different concentration of the lactose (the
substrate) into each of the five test tubes. You should end up with
each test tube containing a different concentration of lactose.
4. Click on the ‘computer screen’ and the experiment will run, and an observation table will pop up.
5. Record the results in the observation table found in the “Observations” part of the lab report.
6. Create a graph to plot the results in the “Observations” part of the lab report. Make sure your graph has a title, with
the axis labelled properly.
7. Report to your teacher when you finish Part 1 before starting Part 2
Observations:
Table 1: Effects of lactose concentration on enzyme activity
Test Tube #
Amount of lactose
substrate (g)
Enzyme Activity:
Number of Molecules of Product
Formed per Minute (x106)
1
2
3
4
5
Graph 1: Effects of lactose concentration on enzyme activity
Part 2: Effect of pH on enzyme activity - Write a set of instructions to determine the effect of pH on enzyme activity.
Procedure:
1. To conduct a controlled experiment, you must determine:
Independent variable: ______________________________
Dependent variable:
______________________________
Controls:
_____________________, ________________________
2. Click on the ____________ controlling the _______ of the solution in which the reaction will take place. You should
end up with each test tube containing a ____________________ pH.
3. Click on the ‘__________________________’ and the experiment will run, and an __________________ will pop up.
4. ___________ the results in the ____________________ table found in the “Observations” part of the lab report.
5. Create a ___________ to plot these results.
Observations:
Fill in the observation table below for Part 2 of the investigation. Remember to create headings for the table and give the
table a name.
Table 2: ___________________________________________________
[
/5 CM]
[
/5 CM]
Test Tube #
1
2
3
4
5
Graph 2: ________________________________________________
Analysis Questions:
Answer the following questions in the space provided. Write in full sentences.
[Total
/10 TI]
1. What happens to the reaction rate as substrate (lactose) concentration increases?
[
/1 TI]
2. Explain why the maximum reaction rate cannot be reached at low lactose concentrations.
[
/1 TI]
3. What does your data indicate about the optimum pH level for this lactase-catalyzed reaction?
[
/1 TI]
4. People with lactose intolerance are able to take products such as Lactaid that contain the lactase enzyme with
their meals. These products can be taken in pill form. Considering the fact that the pill form of the enzyme
would have to travel through the person's stomach (which is very acidic), what special consideration would the
producer of this product need to be concerned about?
[
/2 TI]
5. Enzymes function most efficiently at the temperature of a typical cell, which is 37 degrees Celsius. Increases or
decreases in temperature can significantly lower the reaction rate. Write a detailed procedure & include a
picture describing the test to show how temperature affects enzyme activity. Also state the independent,
dependent and constant variables.
[
/5 TI]
Independent variable: ____________________________
Dependent variable:
____________________________
Controls:
____________________________,
____________________________
Procedure:
Picture