fermentation lab report

fermentation lab report - Ann Forrest Thursday 12:20-2:15...

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Ann Forrest October 20, 2011 Thursday 12:20-2:15 Fermentation Abstract: This experiment was completed in order to show why naturally aged wines are only 12- 14% alcohol, with pretty much the rest being yeast. In order to test this question, we tested the amount of CO2(showing that the yeast was still alive) that was produced in different concentrations of ethanol. Whichever concentration produced the most displacement of the yeast would be the optimal concentration of ethanol in yeast fermentation. Also, we experimented with the production of CO2 over time to show when the yeast was still thriving and when it began to die off. Introduction: Energy is essential to every living organism in life, and most organisms obtain this energy by breaking down molecules and using the energy that is released. This process, called metabolism, occurs in both plants and animals. Both metabolize certain molecules to create energy; the molecule focused on in this lab is the sugar glucose, produced by photosynthesis (Lab Manual 41). The first step of this sugar metabolism is glycolysis, which is the anaerobic catabolism of glucose, and can occur with or without oxygen. It occurs when the bonds of glucose molecules are rearranged. The 6 carbon sugar in glucose is metabolized into 2 molecules of pyruvic acid, each with 3 carbons. Only 2 ATP, the main source of energy in the cell, are created in glycolysis, which is a relatively small amount of energy since ATP cannot be stored for very long. (Raven, Johnson, Mason, Losos, Singer 113)
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Because glycolysis can occur in both the presence and the absence of oxygen, it has two paths it can take after creating ATP. It can be converted into ethanol (alcohol) and carbon dioxide through the alcoholic fermentation pathway, or it can be converted into lactate through the lactic acid fermentation pathway. (Alba-Lois & Segal-Kischinevzky) If oxygen is present, the cell undergoes cellular respiration through the Krebs Cycle and the electron transport chain, which produces 36 ATP. Compared the mere 2 ATP created in Glycolysis, the production of 36 ATP in the Krebs Cycle is significantly greater, due to the presence of oxygen. If there is no oxygen present, the cell must continuously go through glycolysis to keep producing low amounts of energy. In order to do so, it first goes through the anaerobic process of fermentation. Fermentation takes the NADH, a product of glycolysis, and recycles it back into NAD 1 , an electron receptor that needs to be plentiful for glycolysis. So, fermentation doesn’t, in itself, produce any ATP for the cell, but by producing NAD 1 it provides the base for glycolysis to continuously occur, which, in turn, does produce ATP. When alcohol fermentation occurs, its products are ethyl alcohol and CO2, and when fermentation occurs in animals the product is lactic acid. Both alcoholic fermentation and glycolysis are anaerobic fermentation processes that
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