The experiment was conducted to determine the impact different yeast amounts had on yeast fermentation. It was hypothesized that the more yeast added the more CO2 would be produced. The carbon dioxide production was measured in the fermentation of yeast with solution of no yeast in test tube 1, 1mL yeast in test tube 2, and 3mL of yeast in test tube 3 over a period of twenty minutes. All of the yeast amounts produced CO2, but test tube 3 was the most efficient of the three.
Introduction: This lab was to investigate fermentation, a cellular process that transfers the energy in glucose bonds to ATP.
The energy in ATP can then be used to perform cellular work. Fermentation is an anaerobic (without oxygen) process; cellular respiration is aerobic (using oxygen ). All living organisms, including bacteria, produce ATP in fermentation or cellular respiration and then use ATP in their metabolism. (Campbell, 2008) Cellular respiration is a sequence of three metabolic stages: glycolysis (in the cytoplasm) and the Krebs cycle and the electron transport chain in mitochondria.
Fermentation involves glycolysis but doesn’t involve the Krebs cycle and the electron transport chain, which can’t function at low oxygen levels.
Two common types of fermentation are alcoholic fermentation and lactic acid fermentation. Alcoholic fermentation begins with glycolysis, breaking glucose into two molecules of pyruvate with and yielding 2 ATP and 2 NADH molecules. In anaerobic environments, the pyruvate (a 3-carbon molecule) is converted to ethyl alcohol (ethanol, a 2-carbon molecule) and CO2. In this process the 2 NADH molecules are oxidized, replenishing the NAD+ used in glycolysis (Campbell, 2008). In our lab, we investigated alcoholic fermentation in backer’s yeast (a single-celled fungus).
When oxygen is low, some fungi, including yeast and most plants, switch from cellular respiration to alcoholic fermentation (berg, 2002). In our lab, the carbon dioxide (CO2) produced was used as an indication of the relative rate of fermentation taking place. Materials and Methods: We set up 3 fermentation set-ups, labeling them 1, 2, and 3. Then, filled a tub with hot water and inserted the end of the plastic tubing into one of the test tubes and submerged the collection tube and plastic tubing in the tub.
After that, we mixed the fermentation solutions for the other tubes, (tube 1 got 4mL of water and 3mL of corn syrup, tube 2 got 3 mL of water, 1 mL of yeast and 3 mL corn syrup, tube 3 got 1 mL water, 3 mL yeast and 3 mL of corn syrup) . We then mixed each test tube and put the rubber stoppers in the fermentation tubes. Finally, we marked the water level on each collection tube with a wax pencil to use as the baseline. Then at 5 minute intervals we measured the distance from the baseline for 20 minutes.
The different amounts of yeast used in fermentation had a significant impact on the amount of carbon dioxide produced. The tube with 3mL produced the most with a difference of 1. 75mm, while the tube with 1mL produced a difference of 1. 5mm of carbon dioxide. The control with no yeast resulted in 0mm difference of carbon dioxide and was the least productive of the tubes.
Discussion: The hypothesis was supported in that all amounts of yeast produced energy and that 3mL of yeast was the most efficient. The carbon dioxide produced can be directly related to the energy produced through fermentation because carbon dioxide is a by-product of ethanol fermentation. The control that contained no yeast produced no energy because there was no yeast to break down the corn syrup which is required for glycolysis and fermentation to occur. Test tube 3 with 3mL of yeast had the greatest rate of energy production because it had the largest amount of yeast present to break down the corn syrup. The largest source of error for the experiment was the start time of fermentation.
The yeast was added to the 3rd tube after the 2nd tube had begun fermenting. Fermentation takes time to reach its maximum rate of energy production so the time gap left tube 2 further ahead than tube 3 in the fermentation process. The data on rate of carbon dioxide production was therefore off-set because the start of fermentation was not controlled. If this experiment were to be repeated, extra care would be taken to ensure that fermentation began at the same time. Other follow-up experiments may include testing other types of yeasts to see how fermentation rates are impacted.