Background Information: Yeast is a tiny unicellular fungus that obtains energy from outside sources (a heterotroph) mostly sugars in order to grow and reproduce. Yeast is often used in bread dough to make the dough rise. With the presence of oxygen a yeast cell creates energy by performing cellular respiration and producing a high amount of ATP, but when in bread dough the absence of oxygen causes the yeast to perform alcoholic fermentation. The yeast breaks down sugars in the dough through glycolysis and alcohol fermentation and produces a small amount of ATP, will also release carbon dioxide.
The carbon dioxide produced by alcoholic fermentation causes the dough to rise. Carbon dioxide is made by yeast as a waste product and the quantity of carbon dioxide is a sign of growth. Yeast organisms’ size and quick reproduction make them great for testing different factors such as temperature, which is what will be tested in this lab. Purpose and Question: The ideal temperature for yeast growth is between 30 and 35 degrees Celsius depending on the type and if there is a sufficient food source. The lab will test whether yeast would release more carbon dioxide provided that there was sugar at room temperature or in an incubator?
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The incubator will be set at 37 degrees Celsius and the room temperature is 22 degrees Celsius. -Would yeast produce more carbon dioxide with the presence of sugar at room temperature or in an incubator? Hypothesis: -If one syringe is put in the incubator and the other at room temperature then the syringe at room temperature would rise more because the incubator would be too hot for the yeast to adapt as quickly as the syringe set at room temperature. Variables: * Independent variable- Temperature. * Dependent variable- ml of CO2 produced. * Control variables- amount of 25% molasses solution, amount of yeast, and time left to sit. Materials: * 2 ml of yeast suspension. * 20 ml of 25% molasses solution. * 2 60 ml syringes. * Incubator.
* Masking tape. * Lab aprons. * Safety goggles and gloves. Procedure: 1. Mix 1 ml of yeast suspension with 10 ml of 25% molasses solution. 2. Aspirate solution into a 60 ml syringe. Remove all air bubbles. 3. Use masking tape to label the syringe with team name, date, and contents of syringe. 4. Repeat steps 1-3 for second syringe. 5. Place one syringe in the incubator and the other on the counter at room temperature for 3 hours and 25 minutes.
Results: Group name| Sugar %| Light/Dark| Temperature| Ml of CO2 produced after 3 days| Peru| 10% corn syrup| -| RT| 50 ml| Peru| 50% corn syrup| -| RT| >48 ml| Canada| 25% molasses| -| Incubator| >50 ml| Canada| 25% molasses| -| Fridge| 0. 5 ml| Kenya | 25% corn syrup| -| Fridge| 0 ml| Kenya| 25% corn syrup| -| Incubator| 16 ml| Baja| 25% molasses| -| Incubator| >52 ml| Baja| 25% molasses| -| RT| >51 ml| Belize| 50% corn syrup| -| RT| >30 ml | Belize| 50% molasses| -| RT| 3 ml| Mongolia| 25% molasses| Light| RT| 2 ml| Mongolia| 25% molasses| Dark| RT| 0 ml|.
The syringe that was placed at room temperature had produced 1 ml more of carbon dioxide in the short period of time given for the experiment than the syringe placed in the incubator. Actually the syringe placed in the incubator didn’t show any change after two and a half hours. But 3 days later both syringes had popped because of the excessive amount of carbon dioxide produced. Discussion: Glycolysis is an anaerobic process that continues with or without oxygen, glycolysis breaks down glucose into a small amount of ATP molecules.
With the presence of oxygen the products of glycolysis are used to produce many more ATP through cellular respiration. But without oxygen fermentation occurs. Both cellular respiration and alcoholic fermentation produce carbon dioxide. Cellular respiration Alcoholic Fermentation When the yeast for this lab was aspirated into the syringes all air bubbles were removed to create an oxygen-free environment to record the yeast’s reaction. The optimum temperature for yeast growth is 30-35 degrees Celsius providing there is a sufficient food supply.
For the experiment each syringe was set at a different temperature and both syringes contained the same amount of molasses solution, one was set at 22 degrees Celsius and the other at 37 degrees Celsius. The hypothesis made for this experiment was supported by the data recorded; the syringe set at 22 degrees Celsius produced more carbon dioxide in the short period of time given than the syringe set at 37 degrees Celsius. The syringe placed in the incubator was a hotter living environment for the yeast and was harder to adapt to than the syringe set at room temperature.
At high temperatures yeast begins to die which explains why in when bread is baked the yeast inside the dough dies and the alcohol produced also evaporates. Comparing Data: Group name| Sugar %| Temperature| Ml of CO2 produced after 3 days| Canada| 25% Molasses| Fridge| 0. 5 ml| Canada| 25% Molasses| Incubator| >50 ml| Baja| 25% Molasses| RT| >51 ml| Baja| 25% Molasses| Incubator| >52 ml| Both of the syringes placed in the incubator popped from the large amount of carbon dioxide produced from the yeast.
Team Canada’s syringe that was put in the fridge didn’t change very much which concludes that yeast doesn’t grow well at very high or very low temperatures. To elaborate further on the lab experiment, it was difficult to aspirate all of the solution without getting any air bubbles which explains the difference in the starting numbers for the two syringes. To advance the data results it would be better to record the number of ml increased every two hours to have a more organized data table. To improve the lab and further experiments an increase of the % of sugar solution would result in a shorter amount of time required for the project.
Citation: 1. Morton, J. S. (1980). Institute for creation research. Retrieved from http://www. icr. org/article/glycolysis-alcoholic-fermentation/ 2. Pearson Education. (2009, July 7). Phschool. Retrieved from http://www. phschool. com/science/biology_place/biocoach/cellresp/intro. html 3.
Yeast howstuffworks. (n. d. ). Retrieved from http://science. howstuffworks. com/life/fungi/yeast-info. htm 4. Arthur, W. (n. d. ). Thermal adaptation in yeast. Retrieved from http://www. ncbi. nlm. nih. gov/pmc/articles/PMC232826/.