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Yeast can grow in test tubes filled with water. By adding a sugar called sucrose and sealing it with a stopper and a pipette, yeast can even grow in anaerobic, or oxygen deprived, conditions via fermentation, cellular respiration without oxygen using alcohol or lactic acid.
Every organism has a way to create ATP even while lacking oxygen. While fermentation does produce less ATP it still keeps glycolysis going, which at least produces some. So the biological importance of this is teaching about glycolysis , the Krebs Cycle, the Electron Transfer Chain, and its parts.
Does the temperature and/or concrentration of sucrose in the water increase the rate of cellular respiration in yeast?
This lab was completely screwed up. In making the procedure the group was unsure what variable to use and ended up using two and completely messing the results. There was zero consistency and any real data gain from this was only general, very vague comparisons. The 1% at the ideal yeast temperature was the most successful in displacing water. That could mean the package was right and 100 C is the ideal temperature for yeast. Based on the fact that 5% did worse than 1% in the hot test could mean there is an ideal amount of sucrose for efficient ATP production as well. It could also mean the 1% tube was left in the hot water too long by accident. Because of all the error going on, the hypothesis couldn't really be supported or unsupported. Though it can be said that ideal temperature beat cold by a marginal degree, indicating that cellular respiration works better in warm environments. It would be interesting to see how these same things effect aerobic respiration? Does a human create ATP faster when it's warm out?
The hot plate took a long time to heat up, so the test tubes were placed in prematurely and let to sit for a little longer than ten minutes. Some of the test tubes were two small for 25 mL of solution, so there was a lot of changing of tubes, and by consequence some tubes may have been differently shaped or left to heat/cool to long or not long enough. In the end, the results: hot 5% = 10mL; hot 1% = 12 mL; cold 10% = 1/2 mL; cold 5% = 1/2 mL; control 0% = 1/2 mL. The results were converted into rate in mL/minute for the graph and table.
Doherty, Jennifer, & Dr. Waldon, Ingrid. (2008) Cellular Respiration in Yeast. Retrieved from Mr. Landry.
- Filled five test tubes with .75 grams of yeast each.
- Filled one test tube each with 25 mL of: 0%, 1%, and 10% sucrose. Filled two with 5%.
- Placed a stopper and pipette in each tube and shook each to mix the yeast and water.
- Filled a beaker with water and placed it on hot plate. Allowed to come up to 100 Celsius (37 Fahrenheit), which is the ideal temp for yeast, as specified by the back of the package.
- Filled another beaker with ice.
- Filled five graduated gas collectors with water and connected them to the test tubes via the pipettes.
- Placed one 5% and 1% in the heated water.
- Placed the other 5% and 10% in the ice.
- Left the 0% out at room temperature for control.
- Timed ten minutes for each before measuring the amount in grams of CO2 which displaced the water in the graduated gas collectors.
Materials:
-yeast
-water
-sucrose
-test tubes
-hot plate
-thermometer
-beakers
-graduated cylinder
-stoppers
-pipettes
-graduated gas collector
Hypothesis:
If yeast is added to water that has either a higher concentration of sucrose or a higher temperature then the rate of cellular respiration in the yeast will rise, because glycolysis will have more sugar to turn to ATP and/or glycolysis will react faster because it would be in a more habitable environment.
Independent Variable:
Concentration of Sucrose/Temperature
Dependent Variable:
Rate of cellular respiration (amount of CO2 produced)
Control: 0% sucrose; room temperature