2/16/14
Hon Bio Lab Report
The Effect of Water Levels on Cell Respiration
ABSTRACT
In this lab, we mixed yeast, sucrose, and salt with four different water levels to determine how different amounts of water affect the amount of carbon dioxide produced in cell respiration, specifically fermentation.
After viewing the results, we found that only small amounts of carbon dioxide were produced by too much or too little water, while large amounts of carbon dioxide were produced by moderate water levels in between.
INTRODUCTION
To achieve these results, we plugged the test tubes that the substances were in to restrict oxygen from entering, causing fermentation to occur. Fermentation is a form of cell respiration that does not need oxygen and is also known as anaerobic respiration. Cell respiration is the process by which glucose is broken down and ATP is produced.
Fermentation contains the same first step as aerobic respiration, but then takes different routes from there. The first step is known as glycolysis. In glycolysis, the six carbon glucose is broken down into two pyruvates. Essentially what happens is the six carbons are split into two three carbon groups, each called pyruvates. Then, what happens in aerobic respiration is the pyruvates are oxidized, diffused through the outer membrane of the mitochondria, and ultimately, oxygen acts as the final electron acceptor to form water.
Instead of oxygen, yeast fermentation creates ethyl alcohol, which also acts as an electron acceptor, making up for the lack of oxygen. Fermentation also regenerates NAD+, which allows for the process to become a cycle and continue to produce more ATP.
While we didn’t let the substances sit long enough to become alcohol, we let them sit long enough to be able to study the amounts of carbon dioxide produced through this process.
HYPOTHESIS
If the sucrose, yeast, and salt are placed at water levels of 20 ml, 10 ml, and 5 ml, then more carbon dioxide will be released than in the control (35 ml).
MATERIALS
4 graduated cylinders, 4 pieces of paper, 4 test tubes, 4 g of yeast, 4 g of table sugar, .4 g of salt, 70 ml of water, 4 stoppers with syringes attached, 4 stoppers, and a scale.
PROCEDURE
1. We put 35 ml of water into one graduated cylinder, making this the control.
2. We placed 20, 10, and 5 ml of water into three separate cylinders.
3. Next, we poured the water from each of the four graduated cylinders into four test tubes.
4. Using folded pieces of paper, we placed 1 g of yeast, 1 g of sucrose (table sugar), and 0.1 g of salt into each of the four test tubes at the same time for accuracy.
5. We then put stoppers on the test tubes, shook them, switched the stoppers with stoppers with syringes, and let the mixtures sit for 5 minutes.
6. When the 5 minutes was up, we immediately pressed on each of the syringes to study the amounts of carbon dioxide created.
7. From there, we waited one minute, studied the carbon dioxide levels, and then pressed the syringes again.
8. We took three more data points using the method described in Step 7, finishing with a total of five data points.
RESULTS
Water Levels
|
Carbon dioxide produced after 0 min
|
Carbon dioxide produced after 1 min
|
Carbon dioxide produced after 2 min
|
Carbon dioxide produced after 3 min
|
Carbon dioxide produced after 4 min
|
5 ml
|
1.6 ml
|
1.9 ml
|
2 ml
|
3 ml
|
4 ml
|
10 ml
|
5 ml
|
5.1 ml
|
6.3 ml
|
7.4 ml
|
8.6 ml
|
20 ml
|
1.6 ml
|
1.8 ml
|
3.2 ml
|
4.5 ml
|
6.2 ml
|
35 ml
|
1.8 ml
|
1.9 ml
|
2 ml
|
2.2 ml
|
2.4 ml
|
The table above shows the amounts of carbon dioxide produced in the different water volumes and at the different times the syringe was pressed down.
The above graph displays the carbon dioxide produced after the allotted times. The different colored lines represent the different water levels (See key). Note: the 10 ml line is in pen, which is easy to see on paper and somewhat tough to see in a picture. The 10 ml line is slightly darker than the 5 ml line and is the highest line.
CONCLUSION
It is clear to see in the graph above that the moderate volumes of water- at 10ml and 20 ml- were the optimal levels for cell respiration. These volumes also experienced the steepest increase in carbon dioxide production. This is evident in observing that the slopes of 10 ml and 20 ml lines are much greater than the slopes of the 5 ml and 35 ml. While the 5 ml level had some increase in production, it still failed to reach close to the 10 ml and 20 ml. The control, the 35 ml volume, had the least carbon dioxide production and increase over time.
The reason water was used in this experiment was to hydrate the yeast and and allow yeast molecules to move freely through the liquid and react to the sugar. This makes the results unexpected and rejects our hypothesis because we thought that more water meant more reaction and thus more carbon dioxide, but instead, too much water, in the case of the 35 ml control, meant less production and slower increase in carbon dioxide. A similar result came with the 5 ml volume, but at least there was some increase and higher production at that level, allowing us to make the assumption that too much and too little water make for little production of carbon dioxide in fermentation.
Two constants were the sugar and yeast levels, and two potential sources of error were putting the different ingredients in at different times and having slight gaps in the stoppers for oxygen to escape and enter.
CITATION
Helmenstine, Anne Marie. "What Is Fermentation?" About.com Chemistry. N.p., n.d. Web. 18 Feb. 2014.
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