Experimenting with Different pH Levels on Fermentation
Introduction
Background: The purpose of this lab is to figure out how different pH levels affect the expansion of the carbon dioxide during fermentation. "When oxygen is not present, glycolysis is followed by a pathway that makes it possible to continue to produce ATP without oxygen. The combined process of this pathway and glycolysis is called Fermentation" (Miller 262). During anaerobic respiration, carbon dioxide is still released as a byproduct into a solution. This expansion will be visible in a liquid solution. The pH level of the liquid during fermentation could possibly alter the amount of carbon dioxide expansion. "At a pH of 7, the concentration of H+ ions and OH- ions is equal. Pure water has a pH of 7. Solutions with a pH below 7 are called acidic because they have more H+ ions than OH- ions. The lower the pH, the greater the acidity" (Miller 43).
Experimental Design: How does the pH value of the solution that fermentation takes place in, affect the carbon dioxide expansion? The pH level is the independent variable and the dependent variable is the carbon dioxide expansion. Changes in the dependent variable will be measured in centimeters. The control will have 25mL of water (pH 7, basic environment), 3g of yeast, and 2g of sugar.
Hypothesis: If the pH level of the liquid that the fermentation occurs changes, then the expansion of carbon dioxide will be less because the ideal pH level for fermentation to occur in is a pH level of 7.
Methodology and Procedure
1. Prepare 4 different test tubes, each with 25ml of different liquids. One of the test tubes has water, and the other three test tubes contain liquids with pH 10, pH 7, pH 4.5, pH 3 levels respectively. 2. Prepare 3g of yeast and 2g of sugar for each test tube. 3. Put yeast and sugar mixture into each test tube. 4. Draw a line at each mixture's height on the outside of the test tubes. 4. Wait for 10 minutes. 5. Measure height that each liquid increased. 6. Compare the results.
The results were not as expected. When the pH level was 7 and the concentration of H+ ions was equal to OH- ions, fermentation was not the most active. The greatest growth (indicating expansion of carbon dioxide) was in the solution with a pH level of 4.5 (a more acidic level). The fermentation of the solutions with pH levels of 10 and 3 did react as expected with less expansion of carbon dioxide (less growth) than the solution with the pH level of 7. The results suggest that a solution with a pH level of 4.5 is more optimal for the fermentation of yeast.
The results negate the hypothesis: If the pH level of the liquid that the fermentation occurs changes, then the expansion of carbon dioxide will be less because the ideal pH level for fermentation to occur in is a pH level of 7.
The results suggest another hypothesis: If the pH level of the liquid is at a slightly acidic level, then the expansion of carbon dioxide will be the greatest. This explains why Bakers yeast "thrives when the pH is slightly acidic--pH 4.5 is best. However, it will grow over a wide range, even when the pH is slightly basic...it will slow down as the pH gets farther from 4.5...A nuetral to slightly acid pH will give the fastest rate of fermentation" ("How does pH").
Weaknesses/problems in the experimental design: Experimenters could have mixed the pH solutions incorrectly and/or not tested each solution for exact pH level. Also, mistakes could have been made when measuring the amount of glucose and yeast added to each test tube. Another possibility is that the line drawn on each test tube to indicate the height of the solution might not have been drawn accurately.
Limitations: Only four pH levels were used for the fermentation experiment.
Questions to consider for future research: How does the optimal pH level for fermentation change when the amount of yeast is changed? How does the optimal pH level for fermentation change when the amount of glucose is changed?
Works Cited
"How does pH effect yeast fermentation?" Answers.com. Answers Corporation, n.d. Web. 6 Mar. 2014.
Miller, Kenneth R. and Joseph S. Levine. Biology. Boston, MA: Pearson, 2010.
Experimenting with Different pH Levels on Fermentation
Introduction
Background: The purpose of this lab is to figure out how different pH levels affect the expansion of the carbon dioxide during fermentation. "When oxygen is not present, glycolysis is followed by a pathway that makes it possible to continue to produce ATP without oxygen. The combined process of this pathway and glycolysis is called Fermentation" (Miller 262). During anaerobic respiration, carbon dioxide is still released as a byproduct into a solution. This expansion will be visible in a liquid solution. The pH level of the liquid during fermentation could possibly alter the amount of carbon dioxide expansion. "At a pH of 7, the concentration of H+ ions and OH- ions is equal. Pure water has a pH of 7. Solutions with a pH below 7 are called acidic because they have more H+ ions than OH- ions. The lower the pH, the greater the acidity" (Miller 43).
Experimental Design: How does the pH value of the solution that fermentation takes place in, affect the carbon dioxide expansion? The pH level is the independent variable and the dependent variable is the carbon dioxide expansion. Changes in the dependent variable will be measured in centimeters. The control will have 25mL of water (pH 7, basic environment), 3g of yeast, and 2g of sugar.
Hypothesis: If the pH level of the liquid that the fermentation occurs changes, then the expansion of carbon dioxide will be less because the ideal pH level for fermentation to occur in is a pH level of 7.
Methodology and Procedure
1. Prepare 4 different test tubes, each with 25ml of different liquids. One of the test tubes has water, and the other three test tubes contain liquids with pH 10, pH 7, pH 4.5, pH 3 levels respectively.2. Prepare 3g of yeast and 2g of sugar for each test tube.
3. Put yeast and sugar mixture into each test tube.
4. Draw a line at each mixture's height on the outside of the test tubes.
4. Wait for 10 minutes.
5. Measure height that each liquid increased.
6. Compare the results.
Data and Results
Discussion and Analysis
The results were not as expected. When the pH level was 7 and the concentration of H+ ions was equal to OH- ions, fermentation was not the most active. The greatest growth (indicating expansion of carbon dioxide) was in the solution with a pH level of 4.5 (a more acidic level). The fermentation of the solutions with pH levels of 10 and 3 did react as expected with less expansion of carbon dioxide (less growth) than the solution with the pH level of 7. The results suggest that a solution with a pH level of 4.5 is more optimal for the fermentation of yeast.The results negate the hypothesis: If the pH level of the liquid that the fermentation occurs changes, then the expansion of carbon dioxide will be less because the ideal pH level for fermentation to occur in is a pH level of 7.
The results suggest another hypothesis: If the pH level of the liquid is at a slightly acidic level, then the expansion of carbon dioxide will be the greatest. This explains why Bakers yeast "thrives when the pH is slightly acidic--pH 4.5 is best. However, it will grow over a wide range, even when the pH is slightly basic...it will slow down as the pH gets farther from 4.5...A nuetral to slightly acid pH will give the fastest rate of fermentation" ("How does pH").
Weaknesses/problems in the experimental design: Experimenters could have mixed the pH solutions incorrectly and/or not tested each solution for exact pH level. Also, mistakes could have been made when measuring the amount of glucose and yeast added to each test tube. Another possibility is that the line drawn on each test tube to indicate the height of the solution might not have been drawn accurately.
Limitations: Only four pH levels were used for the fermentation experiment.
Questions to consider for future research: How does the optimal pH level for fermentation change when the amount of yeast is changed? How does the optimal pH level for fermentation change when the amount of glucose is changed?
Works Cited
"How does pH effect yeast fermentation?" Answers.com. Answers Corporation, n.d. Web. 6 Mar. 2014.
Miller, Kenneth R. and Joseph S. Levine. Biology. Boston, MA: Pearson, 2010.