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Sugar Fermentation

Figure from experiment 12B from Biology with Vernier

Introduction

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 the aerobic fermentation of sugars is much more efficient, in this experiment we will have yeast ferment the 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 fermentation rate and metabolic activity of the organism.

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

{{\text{C}}_{\text{6}}}{{\text{H}}_{{\text{12}}}}{{\text{O}}_{\text{6}}} \to {\text{2 C}}{{\text{H}}_{\text{3}}}{\text{C}}{{\text{H}}_{\text{2}}}{\text{OH + 2 C}}{{\text{O}}_{\text{2}}}{\text{ + energy}} {\text{glucose }} \to {\text{ ethanol  +  carbon dioxide  +  energy}}

Note that alcohol is a byproduct of this fermentation.

Objectives

In this experiment, you will

  • Use a Gas Pressure Sensor to measure the pressure change caused by carbon dioxide released during fermentation.
  • Determine the rate of fermentation.
  • Determine which sugars yeast can metabolize.

Sensors and Equipment

This experiment features the following Vernier sensors and equipment.

Additional Requirements

You may also need an interface and software for data collection. What do I need for data collection?

Standards Correlations

See all standards correlations for Biology with Vernier »

Experiment 12B from Biology with Vernier Lab Book

<em>Biology with Vernier</em> book cover

Included in the Lab Book

Vernier lab books include word-processing files of the student instructions, essential teacher information, suggested answers, sample data and graphs, and more.

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