9TH GRADE BIOLOGY (Mr. Duane's Class)
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April 08, 2010


Week #6 Oct 9th - 10th:



Lab Experiment Factors that Affect Fermentation of Yeast (Sugar Type)

Record in Lab Notebooks

Experimental Design Diagram




Written Observations


Rates of Fermentation for glucose, lactose, maltose, sucrose, and fructose



Experimental Design Worksheet: Fermentation in Yeast


Lab Procedure: Fermentation in Yeast


Lab Report Template: Fermentation in Yeast



Data: Fermentation in Yeast

Assignment due Friday, Oct 17th:

Write a Formal Lab Report for This Controlled Experiment.






Click Here For the Procedure

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Background:  Yeast are able to metabolize some foods, but not others. In order for an organism to make use of a potential source of food, it must be capable of transporting the food into its cells. It must also have the proper enzymes capable of breaking the food’s chemical bonds in a useful way. Sugars are vital to all living organisms. Yeast are capable of using some, but not all sugars as a food source. Yeast can metabolize sugar in two ways, aerobically, with the aid of oxygen, or anaerobically, without oxygen.

In this lab, you will try to determine whether yeast are capable of metabolizing a variety of sugars. Although aerobic fermentation of sugar is much more efficient, in this experiment we will have yeast ferment sugars anaerobically. When the yeast respire aerobically, oxygen gas is consumed at the same rate that CO2 is produced—there would be no change in the gas pressure in the test tube. When yeast ferment the sugars anaerobically, however, CO2 production will cause a change in the pressure of a closed test tube, since no oxygen is being consumed. We can use this pressure change to monitor the respiration rate and metabolic activity of the organism. A Gas Pressure Sensor will be used to monitor the fermentation of sugar.

The fermentation of glucose can be described by the following equation:

C6H12O6  CH3CH2OH + CO2 + energy

glucose                    ethanol      carbon dioxide

Note that alcohol is a byproduct of this fermentation.


If yeast are given sugar in the absence of oxygen, they will produce alcohol and carbon dioxide and capture 2 ATP of energy through the process of anaerobic respiration (fermentation).  To measure the rate of fermentation, it is easier to measure the amount of carbon dioxide released than to measure the amount of alcohol.  The biology gas pressure sensors and CBL’s will measure gas pressure changes as carbon dioxide is released as a result of the process of anaerobic respiration in yeast.  Living things use a sugar source, broken down into the form of glucose by enzymes, as a fuel to capture enough energy to carry out essential life functions.  Sugars are classified as either monosaccharides or disaccharides.  Monosaccharides include fructose and glucose.  Disaccharides include sucrose, lactose, and maltose.  

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Problem:  Brewers and vintners need to know what kind of sugar is the best sugar for a yeast solution that yields the maximum amount of alcohol.  The source of this sugar is either a grain, vegetable, or fruit.  For instance, the beer making process uses barley and hops as a sugar source, where as wines use grapes as a sugar source.  Those sources consist of different types of sugars (glucose, fructose, sucrose etc.) It is very important that the correct sugar be matched with the yeast in order to produce the beverage of choice.  Your research team will design a controlled experiment to determine what type of sugar will release the greatest amount of carbon dioxide (thus yield the most alcohol) through the process yeast fermentation.   


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Assignment: You will conduct an experiment that tests the effect of sugar type on fermentation in yeast.  You will use CBL's to measure changes in gas pressure as yeast metabolize these sugars.  You will hand in a complete lab report on the experiment.  


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Before beginning:  Visit the Yeast Fermentation Data 1999 - 2001  page in the data base to view data collected from past years.  Write a hypothesis that states which type of sugar will yield the greatest amount of alcohol and release the most amount of carbon dioxide and is supported by background information regarding sugar, yeast, and the process of anaerobic respiration (fermentation).


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Handouts for Fermentation of Yeast Experiment:

Background & Experimental Design Worksheet

Lab Handout: Fermentation of Yeast

Lab Report Guidelines 

Data table (blank)

Lab Report Template

Peer Edit Checklist (complete)

Yeast Fermentation Data 1999-2001

Rates of Fermentation: 2002