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Experiment to Investigate the Action of Bile Salts on Fat in Milk

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Experiment to Investigate the Action of Bile Salts on Fat in Milk Planning Variables Temperature - room temperature Full cream milk concentration - 2.5 cm3 per test tube Bile salts concentration - We will investigate this variable at different values Lipase concentration - 0.5 cm3 per test tube Sodium carbonate - 3.5 cm3 per test tube Distilled water - This will vary according to the amount of bile salts in each tube Phenolphthalein - 3 drops We can easily change the concentrations of bile salts by changing the amount of bile salts in each test tube. We can easily keep the temperature constant by doing all the experiments at the same time in the same part of the laboratory. Because we are going to work at room temperature this will keep the temperatures roughly similar. We have chosen room temperature because it is the easiest temperature to keep constant. We are using test tubes to carry out the experiment in so the values of the milk, lipase and sodium carbonate work best at this scale. We will use 3 drops of phenolphthalein as it is only an indicator and so does not need to be measured very accurately and 3 drops will show the colour change clearly enough. ...read more.


Phenolphthalein is pink/purple in acid and clear in alkali. We will use the syringes to add the rest of the necessary liquids. The lipase is the enzyme that will break down the fat in the milk. We will use full cream milk as it has more fat content. The milk will all be taken from the same carton to ensure that the experiment is a fair test. The bile salts are emulsifiers; they will break down the fats and so increase the surface area of the fat droplets. We will use distilled water to keep concentrations in all tubes equal. Distilled water is purer than tap water and so better for this experiment. The sodium carbonate is added to make the solution alkaline to begin with so the colour change is obvious. We will use the stopwatch to find the amount of time it takes for the solutions in the test tubes to turn cloudy white. Test Tube 1 Test Tube 2 Test Tube 3 Test Tube 4 Test Tube 5 Lipase 0.5 cm3 0.5 cm3 0.5 cm3 0.5 cm3 0.5 cm3 Milk 2.5 cm3 2.5 cm3 2.5 cm3 2.5 cm3 2.5 cm3 Sodium Carbonate 3.5 cm3 3.5 cm3 3.5 cm3 3.5 cm3 3.5 cm3 Bile Salts 0 cm3 0.1 cm3 0.25 cm3 0.4 cm3 0.5 cm3 Water 0.5 cm3 0.4 cm3 0.25 cm3 0.1 cm3 0 cm3 Phenolphthalein ...read more.


All we would need to do would be to keep the amount of bile salts and distilled water fixed. I would keep the amount of bile salts fixed at 0.5 cm3 so that the reaction does not take too long. We would not need to add any distilled water as there is water contained in the milk. We could use 5 test tubes and test at 20�C, 30�C, 37�C, 45�C and 55�C. We would use water baths to regulate the temperature in each test tube. However the disadvantages are that a water bath is not very accurate and takes a long time to warm up. Also it is hard to make sure that the contents of the test tubes are the same temperature as the water outside the test tubes. I would expect the test tube at 37�C to react the fastest as this is body temperature and therefore the temperature that lipase normally works at in the small intestine. At lower temperatures the enzymes have less energy and so works slower and at higher temperatures some of the enzymes become denatured and so do not work therefore the reaction is slower. If I drew a graph of temperature versus rate of reaction with temperature on the horizontal axis and rate of reaction on the vertical axis I would expect the graph to rise steeply from 20�C to 37�C and then to decline rapidly from 37�C to 55�C. ?? ?? ?? ?? Ahmed Luqman page 1 ...read more.

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