The Effects of Alcohol Concentration on the Fermentation Ability of Yeast

The Effects of Alcohol Concentration on the Fermentation Ability of Yeast

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The Effects of Alcohol Concentration on the Fermentation Ability of Yeast by Rebecca A. Miller GTA: Xiaobo Guo Course: General Biology Lab CRN: 1115 Date: November 5, 2007
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INTRODUCTION All organisms need energy in order to survive. Autotrophs make their own energy by converting sunlight into chemical energy. Other organisms metabolize molecules in order to attain the energy that is necessary for survival. One of the most common molecular sources of energy is the sugar molecule. Sugar is metabolized in two ways, either by passing through the Krebs Cycle and the Electron Transport Chain or by going through the process of fermentation. However, before either of the two can take place, glycolysis must occur. Glycolysis is the breaking down of a 6-carbon sugar molecule into 2 pyruvate molecules. Glycolysis yields only 2 molecules of ATP and can occur with or without the presence of oxygen. After glycolysis has occurred, the sugar molecules will be broken down further, if oxygen is present, by going through the Krebs Cycle and then through the Electron Transport Chain, which yields much more ATP than the glycolysis, in fact, it yields 32 more molecules of ATP than glycolysis does. If, however, oxygen is not present, then fermentation will take place in order to conserve NAD+ so that glycolysis can continue. The end result of fermentation is carbon dioxide and ethyl alcohol (or lactic acid in animals). Yeasts are organisms that, in the absence of oxygen, will create the energy needed to survive by undergoing fermentation, and thereby producing carbon dioxide and alcohol. In this experiment, it was hypothesized that a higher alcohol concentration beforehand would effect the fermentation of yeast.
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MATERIALS AND METHODS Materials: 1.) 6 small test tubes with only one open end 2.) 1 100mL beaker 3.) Yeast solution (100mL warm water, a pinch of salt, a level spoonful of sugar, and
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This note was uploaded on 04/02/2008 for the course BIOL 1115 taught by Professor Dcscott during the Fall '07 term at Virginia Tech.

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The Effects of Alcohol Concentration on the Fermentation Ability of Yeast

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