MASSACHUSETTS INSTITUTE OF Technology
Department of Biology
TW 2014 Biofuel
Effect of Type of Sugar on Yeast Fermentation*
Summary |
During this lesson, students will be investigating the process of fermentation by
measuring the amount of gas pressure produced by yeast metabolizing a specific
sugar. Students will also measure the pH at the beginning and the end of the
experiment. Since fermentation produces carbon dioxide as a byproduct, some
will dissolve in solution to produce carbonic acid resulting in a lower pH. The
broader concept here is the process of cellular respiration and how it works in
living organisms (yeast). Students should understand that almost all living
things need to process a form of sugar in order to make energy.
Each group of students will be given a specific sugar to add to their yeast
solutions and measure gas pressure over time immediately following the
addition of the sugar. In addition, an “unknown” sugar will be given to each lab
group for identification.
Skills practiced during this lab include: (adapted from scientific
inquiry standards – MA State Frameworks)
 Observe the world from a scientific perspective.
 Pose questions and form hypotheses based on personal observations and knowledge.
 Articulate and explain the major concepts being investigated and the purpose of an
investigation (in lab report)
 Employ appropriate methods for accurately and consistently making observations,
making and recording measurements at appropriate levels of precision,
and collecting data or evidence in an organized way
 Properly use instruments, equipment, and materials (e.g., probeware, meter sticks,
computers)
 Follow safety guidelines.
 Represent data and relationships between and among variables in charts and graphs.
 Use appropriate technology (e.g., graphing software) and other tools.
 Assess the reliability of data and identify reasons for inconsistent results, such as
sources of error or uncontrolled conditions.
 Use results of an experiment to develop a conclusion to an investigation that
addresses the initial questions and supports or refutes the stated hypothesis.
 State questions raised by an experiment that may require further investigation.
 Develop descriptions of and explanations for scientific concepts that were a focus of
one or more investigations.
 Review information, explain statistical analysis, and summarize data collected and
analyzed as the result of an investigation. (in lab report)
Bethany Spinks 2014
*lab adapted from Lab 16B Effect of Temp. on Fermentation by Vernier
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MASSACHUSETTS INSTITUTE OF Technology
Department of Biology
TW 2014 Biofuel



Explain diagrams and charts that represent relationships of variables.
Construct a reasoned argument and respond appropriately to critical comments and
questions.
Use language and vocabulary appropriately, speak clearly and logically, and use
appropriate technology (e.g., presentation software) and other tools to present findings.
Background Information
All living things need energy to live, grow and reproduce. Most living things
produce energy (ATP) through a process called cellular respiration. During this
process, sugar is broken down in cells (by many enzymes) to release energy.
An example of an organism that uses cellular respiration is yeast. Yeasts are single
cell eukaryotic fungi that can process sugar both anaerobically (without oxygen) and
aerobically (with oxygen). You will observe yeast metabolize sugars under anaerobic
conditions (fermentation) and monitor the change in air pressure due to carbon dioxide released
by the yeast. When yeast burn sugar under anaerobic conditions, ethanol (ethyl alcohol) and
carbon dioxide are released as shown by the following reaction:
 2 CH3CH2OH + 2 CO2 + energy
C6H12O6 
glucose
ethanol
carbon
dioxide
Thus, the metabolic activity of yeast may be measured by monitoring the pressure of gas in the
test tube. If the yeast were to respire aerobically, there would be no change in the pressure of gas
in the test tube, because oxygen gas would be consumed at the same rate as carbon dioxide is
produced. In addition, you will also be testing different sugars to see if the yeast are able to
metabolize them. Also, an initial and final pH measurement will be taken as an additional
indication of the rate of fermentation. As the carbon dioxide level increases in the tube, some
will be dissolved in the solution. As a result, carbonic acid is produced.
Bethany Spinks 2014
*lab adapted from Lab 16B Effect of Temp. on Fermentation by Vernier
2
MASSACHUSETTS INSTITUTE OF Technology
Department of Biology
TW 2014 Biofuel
Key Concepts




Cellular respiration
Enzyme Activity
Fermentation
Chemical reactions
Objectives

Use a Gas Pressure Sensor to measure the change in pressure due to CO2 release during
fermentation.
 Determine the rate of fermentation of yeast using different sugars.
 Identify an unknown sugar based on class results.
Biology, High School Course- MA State Frameworks
1.3 Explain the role of enzymes as catalysts that lower the activation energy of biochemical
reactions. Identify factors, such as pH and temperature that have an effect on enzymes.
2.4 Identify the reactants, products, and basic purposes of photosynthesis and cellular
respiration. Explain the interrelated nature of photosynthesis and cellular respiration in
the cells of photosynthetic organisms.
Broad Unit Objectives- Hopkinton High School 10th grade Biology
(MCAS course)
Enduring Understandings
1. Chemical elements form organic molecules that interact to perform the basic
functions of life.
2. Photosynthesis and cellular respiration are interrelated metabolic processes,
essential to life on earth.
Essential Questions
1. How do living things make and use energy?
2. How do the structures of a cell allow it to make and use energy?
•
•
•
•
Observe yeast fermentation.
Identify an unknown sugar through the fermentation protocol.
Record gas pressure over time and measure pH before and after experiment.
Demonstrate knowledge of the process of fermentation and enzyme activity.
Bethany Spinks 2014
*lab adapted from Lab 16B Effect of Temp. on Fermentation by Vernier
3
MASSACHUSETTS INSTITUTE OF Technology
Department of Biology
TW 2014 Biofuel
• Communicate results of the lab clearly through a well-written lab report.
QUESTION OF THE LAB: WHAT EFFECT DOES THE TYPE OF SUGAR
HAVE ON THE RATE OF FERMENTATION OF YEAST?
HYPOTHESIS: Answer the question above in the form of a hypothesis
based on your prior knowledge.
______________________________________________________________________________
MATERIALS
LabPro interface
Palm handheld
Data Pro program
Vernier Gas Pressure Sensor
Graphical Analysis or Logger Pro
(optional)
5% glucose solution
5% sucrose solution
5% fructose solution
5% lactose solution
5% maltose solution
rubber-stopper assembly
1 liter beaker (for water bath)
10 mL pipet or graduated cylinder
18  150 mm test tube
600 mL beaker
vegetable oil in a dropper bottle
pipet bulb or pump
ring stand
yeast suspension
Thermometer
pH paper
basting bulb or Beral pipet
utility clamp
Microscope slide
Bethany Spinks 2014
*lab adapted from Lab 16B Effect of Temp. on Fermentation by Vernier
4
MASSACHUSETTS INSTITUTE OF Technology
Department of Biology
TW 2014 Biofuel
PROCEDURE
PART 1
1. Connect the plastic tubing to the valve on the Gas Pressure Sensor.
2. Plug the Gas Pressure Sensor into Channel 1 of the LabPro interface. Connect the handheld
to the LabPro using the interface cable. Firmly press in the cable ends.
3. Prepare a water bath for the yeast. A water bath is simply a large beaker of water at a certain
temperature. This ensures that the yeast will remain at a constant and controlled temperature.
To prepare the water bath, obtain some warm and cool water from your teacher. Combine the
warm and cool water into the 1 liter beaker until it reaches the temperature you were
assigned. The beaker should be filled with about 600 – 700 mL water. Place the thermometer
in the water bath to monitor the temperature during the experiment.
4. Using a 10 mL pipette or graduated cylinder, transfer 2.5 mL of the
SUGAR SOLUTION GIVEN TO YOU BY YOUR TEACHER into a
clean test tube. Record the type of sugar in data table 1. (If you were
assigned the control no sugar will be added). Label this test tube 1.
5. Gently swirl the yeast suspension to mix the yeast that settles to the
bottom. Transfer 2.5 mL of yeast into test tube 1. Gently mix the yeast into
the sugar solution. Be gentle with the yeast—they are living organisms!
6. Gently pipette a drop of the yeast/sugar solution onto a microscope slide.
Test the pH of the solution by dipping the indicator paper into the drop.
Record in Data Table 1.
7. In the test tube, place enough vegetable oil to completely cover the surface
of the yeast/sugar mixture as shown in Figure 3. Be careful to not get oil
on the inside wall of the test tube. Set the test tube in the water bath.
8. Insert the single-holed rubber-stopper into the test tube. Note: Firmly twist
the stopper for an airtight fit. Secure the test tube with a utility clamp and
ring-stand as shown in Figure 1.
9. Incubate the test tube for 10 minutes in the water bath. Be sure to keep the
temperature of the water bath constant. If you need to add more hot or cold water, first
remove about as much water as you will be adding, or the beaker may overflow. Use a
basting bulb to remove excess water.
Note: Be sure that most of the test tube is completely covered by the water in the water bath.
The temperature of the air in the tube must be constant for this experiment to work well.
10. While one team member is performing Step 8, another team member should prepare the
handheld and interface for data collection. Press the power button on the handheld to turn it
on. To start Data Pro, tap the Data Pro icon on the Applications screen. Choose New from the
Data Pro menu or tap
to reset the program.
Bethany Spinks 2014
*lab adapted from Lab 16B Effect of Temp. on Fermentation by Vernier
5
MASSACHUSETTS INSTITUTE OF Technology
Department of Biology
TW 2014 Biofuel
11. Set up the handheld and interface for a Gas Pressure Sensor.
a. If the handheld displays PRESS(kPa) in CH 1, proceed directly to Step 11. If it does not,
continue with this step to set up your sensors manually.
b. Tap
on the Main screen.
c. Tap
to select Channel 1.
d. Choose PRESSURE-GPS (kPa) from the sensor menu.
e. Tap
to return to the Main screen.
12. When incubation has finished, connect the free-end of the plastic tubing to the
connector in the rubber stopper as shown in Figure 4.
13. Tap
to begin data collection. Maintain the temperature of the water bath
during the course of the experiment. Record the average temperature of the water
bath in Table 1.
14. Data collection will end after 15 minutes. Monitor the pressure readings displayed
on the handheld screen. If the pressure exceeds 130 kilopascals, the pressure inside
the tube will be too great and the rubber stopper is likely to pop off. Disconnect
the plastic tubing from the Gas Pressure Sensor if the pressure exceeds
130 kilopascals.
15. When data collection has finished, an auto-scaled graph of pressure vs. time will
be displayed on the handheld screen. To examine the data pairs on the displayed
graph, tap
or any data point. As you move the examine line, the pressure values of each
data point are displayed to the right of the graph.
16. Determine the rate of fermentation for the curve of pressure vs. time. The rate of
fermentation can be measured by examining the slope of the pressure vs. time curve:
a. Tap the Selection button, .
b. Tap on the data point at the beginning of the sloping portion of the graph to define the left
boundary of the selection. An arrow (>) is displayed on this line.
c. Tap on the data point at the end of the sloping portion to define the right boundary. An
arrow (<) is displayed on this line.
d. Tap
, then tap
.
e. From the Fit Equation menu, choose Linear. The linear-regression statistics for these two
data columns are displayed for the equation in the form
y = ax + b
where x is time, y is pressure, a is the slope, and b is the y-intercept. Note: The
correlation coefficient, r, indicates how closely the data points match up with (or fit) the
regression line. A value of 1.00 indicates a nearly perfect fit.
f. Record the slope of the line (rate of fermentation) in Table 1.
g. Tap
to display the regression curve on the graph of pressure vs. time. Tap
return to the Graph screen.
Bethany Spinks 2014
*lab adapted from Lab 16B Effect of Temp. on Fermentation by Vernier
to
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MASSACHUSETTS INSTITUTE OF Technology
Department of Biology
TW 2014 Biofuel
17. When data collection is complete, disconnect the plastic tubing from the Gas
Pressure Sensor. Using a pipette, remove a small drop of the yeast/sugar solution and place
on a microscope slide. Test the pH of the solution by placing the indicator strip in the drop.
Record the result in Data table 1.
PART 2
Repeat the Part 1 procedure but label a second test tube #2. An unknown sugar
will be assigned to you. Record your data in Data Table 2. Use the class data
google spreadsheet to determine the unknown sugar.
DATA
Data Table 1
Type of Sugar
pH
Avg. Temp (C)
Rate of
Fermentation
(kPa/min)
Initial pH
Final pH
Data Table 2
Type of Sugar
pH
Avg. Temp (C)
Rate of
Fermentation
(kPa/min)
Initial pH
UNKNOWN
Final pH
CLASS DATA SHEET
Bethany Spinks 2014
*lab adapted from Lab 16B Effect of Temp. on Fermentation by Vernier
7
MASSACHUSETTS INSTITUTE OF Technology
Department of Biology
TW 2014 Biofuel
QUESTIONS:
1. What is the purpose of the control tube?
2. What is the purpose of the vegetable oil?
3. According to the class data, what sugar could the yeast metabolize
the best?
4. Hypothesize why some sugars are not utilized by yeast while other sugars are
metabolized.
5. According to the class data, what was the unknown sugar?
6. How do the pH levels relate to the rate of fermentation?
7. Explain the sources of error in this lab.
8. Was your hypothesis supported or refuted by the data collected?
9. Write a full lab report according to the format and rubric below.
Assessment- Lab Report
HHS Science Dept Lab report Format
Biology Team Lab Report Rubric
Additional Resources
How Stuff Works- Yeast
BioCoach - Fermentation
Extensions:
Got time?
If you have time before your presentation, it would be helpful to provide:
• Relevant content standards—National Science Education Standards:
http://www.nap.edu/readingroom/books/nses/html/6a.html
• Science skills (using the Essential Science Skills grid on the FrontPage under
Other Resources)
• Key concepts, according to the AAAS benchmarks, which provide a framework for
K-12 expectations:
http://www.project2061.org/publications/bsl/online/bolintro.htm
Bethany Spinks 2014
*lab adapted from Lab 16B Effect of Temp. on Fermentation by Vernier
8
MASSACHUSETTS INSTITUTE OF Technology
Department of Biology
TW 2014 Biofuel
Bethany Spinks 2014
*lab adapted from Lab 16B Effect of Temp. on Fermentation by Vernier
9