Accelerated Biology
Name:_________________________
Date:____________
Alcoholic Fermentation in Yeast
Introduction:
All organisms need to extract energy from food, which they use to power growth, reproduction
and other metabolic processes. There are two ways that organisms can extract energy from food:
aerobic and anaerobic cellular respiration. Most organisms use aerobic cellular respiration, which uses
oxygen to release energy from carbohydrates. In fact, the cells in your body are doing aerobic
respiration as we speak. The general equation is shown below:
Aerobic Respiration
Carbohydrates + Oxygen → Carbon Dioxide + Water + Energy
Aerobic respiration is a great process, because it extracts a lot of energy from carbohydrates. For
example in aerobic respiration, one glucose molecule can produce enough energy to fill 38 ATP
molecules! Because it is an efficient process, most organisms depend on oxygen to carry out aerobic
cellular respiration.
How do organisms make energy if they do not have oxygen? They carry out anaerobic respiration
or fermentation. Anaerobic respiration releases energy from food when there is no oxygen. However, it
is not very efficient, and organisms try to avoid carrying it out. For example during fermentation, one
glucose molecule can produce enough energy to fill only 2 ATP molecules. That’s 36 ATP less than with
oxygen! Human muscle cells carry out aerobic respiration whenever possible. When you are exercising
really hard, your breathing rate increases to provide more oxygen to the cells. However, if oxygen isn’t
delivered fast enough to your muscle cells, they carry out lactic acid fermentation, a type of anaerobic
respiration. The lactic acid produced causes burning and pain in the muscles. Although your muscle cells
would prefer to get their energy from aerobic respiration, they will do anaerobic lactic acid fermentation
to get some energy to survive.
The type of fermentation we will be studying today is alcoholic fermentation. Yeast cells carry
this out when they are deprived of oxygen.
Anaerobic Respiration: Alcoholic Fermentation
Carbohydrates → Carbon Dioxide + Ethanol + Energy
Humans take advantage of alcoholic fermentation when making bread, cheese, and even when
producing fuel!
Your Task:
The federal government’s Office of Energy Efficiency & Renewable Energy is looking to create
ethanol for cars efficiently and at low cost. A senior scientist feels as though it would be advantageous
to take advantage of the process of alcoholic fermentation. Yeast will rapidly undergo alcoholic
fermentation when placed under appropriate conditions and large amounts of ethanol can be produced.
The senior scientist has hired you as part of the team to test this hypothesis. You will need to take
several steps to complete the assignment:
1. Design an apparatus to measure the rate of fermentation (aka. fermenter)
2. Test your apparatus
3. Design and conduct a controlled experiment to test which environmental conditions lead to the
greatest rate of fermentation
4. Report your findings
Part 1: Design and Test your Apparatus
With your research group, you will need to create a fermenter, an apparatus in which fermentation can
occur and be measured. Remember that the rate of a chemical reaction can be determined by measuring
the rates of at which reactants are used or products are made. You will be given a variety of materials
with which you can construct your fermenter. Discuss with your teacher if additional materials are
needed. Once your apparatus has been designed and created, fill it with a yeast and sugar solution to
test if you are able to measure the rate of fermentation.
Materials Available for Apparatus Design
Various Sizes of Test tubes Rubber Stopper (with and without holes)
Glucose Solution
Yeast
Various Sizes of Flasks
Glass Tubing
Balloons
Various Sizes of Beakers
Measuring Tape
After testing your apparatus:
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Draw your fermentation apparatus in your lab notebook. Label the components of your apparatus
and provide an annotation that explains how it collects data about the rate of fermentation.
Part 2: Design and Conduct an Experiment
Now that you have designed your fermentation apparatus, you will be determining the ideal
environmental conditions for ethanol production by yeast. Your group will decide on the environmental
factor that you will be testing for your experiment. Your experiment must be controlled and measure
the rate of fermentation. Remember that fermentation is an enzyme controlled process, therefore
you may want to consider the factors that affect enzyme function when choosing your environmental
factor. You will be writing a formal lab report to present your apparatus and findings.
Materials Available:
Beakers
Hot plate
Ice
Thermometer
Glucose
Fructose
Lactose
Sucrose
Brewer’s Yeast Baker’s Yeast
Hydrochloric Acid
Rapid Rise Yeast
Yeast Cake
Sodium Hydroxide
In your lab notebook, clearly identify all of the following:
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Purpose

Control group
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Hypothesis

Materials needed
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Independent Variable

Step-by-step procedure
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Dependent Variable

Data table(s)
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Variables that will remain constant
Reporting Your Results
Part 1: Poster
In your groups, you will create a digital CER poster to share your results with the class. Then your
classmates will provide feedback on your results. Use this feedback to help clarify your information
and conduct additional research if necessary.
Part 2: Investigative Report
Individually, you will use the poster, peer feedback, and other addition resources to write your
investigative report. Follow the general guidelines of 2 pages maximum with 12 point font. You
should imbed your data and/or data analysis into your 2 pages to support your writing. A third page
may be added to include your works cited. Any content other than your works cited that shows up
on that third page will not be counted.
Your investigative report should include the following 3 sections:
1. What were you trying to do and why?
2. What did you do during your investigation and why did you conduct your investigation in this
way?
3. What is your argument?
Summary of Lab Notebook Requirements:
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Purpose
Hypothesis
Variables and controls
Materials
Procedure
Labeled drawing of apparatus
Data table(s)