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Using Different Carbon Sources For Growth.

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Using Different Carbon Sources For Growth Introduction: The purpose of this practical is to investigate the ability of yeast to utilize different carbon sources as substrates for respiration. A range of different carbohydrates is used as carbon sources and relatives rates of respiration will be determined by measuring the production of acid by the yeast cells: the faster the rate of respiration, the faster the rate of acid production. Apparatus: * 2% (aqueous solutions of the following sugars: glucose, fructose, galactose, sucrose, lactose, maltose * Top pan balance * Dried yeast granules * Seven 500cm3 flasks, with cotton wool plugs * Ammonium phosphate and ammonium sulphate * Incubator, or water bath, set at 25�C * Burette and stand * 0.1mol dm-3 sodium hydroxide solution * Conical flasks for titration * 25cm3 volumetric pipette and filler * Phenolphthalein indicator solution Method: * Add 200cm3 of each sugar solution to separate, appropriately labelled flasks. ...read more.


Glucose (monosaccharide) Sucrose (disaccharide - fructose and glucose) Maltose (disaccharide - glucose and glucose) Lactose (disaccharide - glucose and galactose) Galactose (monosaccharide) I think that fructose will be the most useful substrate for respiration because it is commonly found in citrus fruits where yeast cells are also abundant and therefore it is readily available. Fructose is also a monosaccharide and therefore does not need to be hydrolysed by an enzyme. Glucose is also a monosaccharide and therefore no enzyme is required. Glucose is also used directly in the glycolysis pathway that is used to produce ATP, which is of course, the point of respiration. I have decided to put sucrose next because only one enzyme is needed to hydrolyse it to form glucose and fructose, which can then be used by the yeast cells for the reasons mentioned above. However the use of an enzyme to break down sucrose means that energy is required to make this enzyme and so both fructose and glucose would appear to be a more useful carbon source. ...read more.


Final (cm3) Volume Added (cm3) Average (1 and 2 only) (cm3) Maltose Rough 0.0 11.0 11.0 10.65 1 11.0 21.8 10.8 2 21.8 32.3 10.5 Lactose Rough 0.0 2.5 2.5 2.20 1 2.5 4.6 2.1 2 4.6 6.9 2.3 Galactose Rough 7.0 13.5 6.5 6.55 1 13.5 20.0 6.5 2 20.0 26.6 6.6 Sucrose Rough 3.0 18.4 15.4 14.30 1 18.4 32.7 14.3 2 32.7 47.0 14.3 Fructose Rough 27.6 44.0 16.4 16.05 1 12.5 28.4 15.9 2 28.4 44.6 16.2 Glucose Rough 0 14.3 14.3 15.90 1 14.3 28.4 14.1 2 25.9 43.6 17.7 This is a bar chart to show the volume of alkali required to neutralize the acid produced by yeast in each sugar solution. From the results that I obtained, I can see that fructose produced the fastest rate of respiration and lactose produced the slowest rate. These results show that my original hypothesis was almost to perfection, however the experiment carried out shows that galactose and lactose have switched places in the list. Neal Desai U6AA Biology Mr. Cooksey ...read more.

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