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Statistical Technique.

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Introduction

Statistical Technique The Mann-Whitney U Test will be used as differences between two treatments (two carbohydrates, sucrose and glucose) are being investigated and measurements have been taken at least six times with each treatment. Random sampling will therefore be useful and the data summarised using the median. Results Table: This table shows the volume of gas collected in five minutes in cm from each carbohydrate . Starch Sucrose Lactose Glucose 0 4 0 4 0 3 0 6 0 3 0 6 0 3 0 4 0 2 0 5 0 3 0 4 As neither starch nor lactose produced any result they shall not be investigated in the statistical test. Null Hypothesis: there is no difference between the volume of gas produced by sucrose or by glucose. Data set A: Rankings 7.5 3.5 3.5 3.5 1 3.5 Data set A: Observations 4 3 3 3 2 3 Data set B: Rankings 7.5 11.5 11.5 7.5 10 7.5 Data set B: Observations 4 6 6 4 5 4 Ra = 22.5 Na = 6 Nb = 6 Rb = 55.5 Ra + Rb = [(Na + Nb)(Na + Nb + 1)] = Ra + Rb = 78 2 Ua = NaNb + Nb(Nb + 1) - Rb = Ua = 36 + 21 - 55.5 = 1.5 2 Ub = NbNa + Na(Na + 1) ...read more.

Middle

The disaccharide molecules lactose and sucrose consist of glucose and fructose and galactose respectively. They therefore only have one glycosidic link that needs to by hydrolysed in order for glucose to be obtained and fermentation occur. If the enzyme necessary for hydrolysis of the glycosidic link is present fermentation can occur. If the enzyme is present it would therefore be expected for each disaccharide to produce a significant amount of carbon dioxide in the time given, although not as much as glucose itself The enzyme that will hydrolyse the glycosidic links in sucrose is present in yeast, however no fermentation will occur with lactose as it does not contain the galactosidase (lactase) enzyme to hydrolyse the glycosidic link to form galactose and glucose. Glucose as a monosaccharide is already in its monomer unit and does not need to undergo any hydrolysis before it reacts. It can therefore begin fermenting immediately and subsequently produces the greatest volume of gas within the timed period. . Fermentation is also an example of anaerobic respiration. In the absence of oxygen the Krebs cycle and the electron transport chain cannot function, only glycolysis takes place. This produces a little ATP: two molecules of ATP for each molecule of glucose and two pairs of hydrogen ions which must be removed if glycolysis is to continue. Fermentation occurs when these molecules are accepted by the pyruvate formed at the end of glycolysis, to give ethanol. ...read more.

Conclusion

Both alcoholic fermentation and glycolysis are anaerobic fermentation processes that begin with the sugar glucose. Glycolysis requires 11 enzymes which degrade glucose to lactic acid (Fig. 2). Alcoholic fermentation follows the same enzymatic pathway for the first 10 steps. The last enzyme of glycolysis, lactate dehydrogenase, is replaced by two enzymes in alcoholic fermentation. These two enzymes, pyruvate decarboxylase and alcoholic dehydrogenase, convert pyruvic acid into carbon dioxide and ethanol in alcoholic fermentation. The most commonly accepted evolutionary scenario states that organisms first arose in an atmosphere lacking oxygen.1,2 Anaerobic fermentation is supposed to have evolved first and is considered the most ancient pathway for obtaining energy. There are several scientific difficulties, however, with considering fermentations as primitive energy harvesting mechanisms produced by time and chance. First of all, it takes ATP energy to start the process that will only later generate a net gain in ATP. Two ATPs are put into the glycolytic pathway for priming the reactions, the expenditure of energy by conversion of ATP to ADP being required in the first and third steps of the pathway (Fig. 2). A total of four ATPs are obtained only later in the sequence, making a net gain of two ATPs for each molecule of glucose degraded. The net gain of two ATPs is not realized until the tenth enzyme in the series catalyzes phosphoenolpyruvate to ATP and pyruvic acid (pyruvate). This means that neither glycolysis nor alcoholic fermentation realizes any gain in energy (ATP) until the tenth enzymatic breakdown. Fig. 1. A comparison of two anaerobic energy-harvesting mechanisms. ...read more.

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