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The Action of Lipase and Bile Salts On Milk

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THE ACTION OF LIPASE AND BILE SALTS ON MILK AIM To investigate the effect of temperature upon the action of lipase. Lipase is an enzyme that digests or breaks down fat into fatty acids and glycerol. FACTORS INVOLVED All factors will be kept constant with the exception of temperature that will be varied. The factors to remain constant include: * Concentration of the lipase enzyme * Concentration of bile salts * Volume of milk in each test tube * Volume of phenol phthalein used * Volume of NaCO3 * Concentration of NaCO3 FAIR TEST A syringe will be used to put the bile salts into each test tube. The same syringe will be used for each test tube. This is to prevent cross-contamination as the syringe will only contain bile salts. Similarly a single syringe will be used to put the enzyme into each test tube. Again this is to prevent cross-contamination as this syringe will only contain the enzyme. Immediately after the enzyme is added the solution will be stirred thoroughly. This is to encourage all of the enzyme to come into contact with the fat and the bile salts. ...read more.


PLAN Two test tubes will be placed in water baths at the following temperatures: 10 degrees; 20 degrees; 30 degrees; 60 degrees and 80 degrees. Two test tubes will be left at room temperature. The average time taken for each of the two tubes at each temperature will then be taken. Each test tube will be left in the water bath for 3 minutes. METHOD In each of the 10 test tubes we added 3 cm3 of milk, 3 cm3 NaCO3, 5 drops of phenolphthalein and 1 cm3 bile salts. 1 cm3 of lipase enzyme was placed in each of the water baths and left to reach the temperature of the water. After the lipase had been in the water baths for 3 minutes it was added to each of the test tubes. The two test tubes being tested at room temperature also had 1 cm3 of lipase added. The time taken for the colour of the solution to change from pink to white was taken using a stop clock. RESULTS The results of the experiment are set out in the following table: Test Tube Temp (?C) ...read more.


The Phenol Phthalein was used because it is an indicator which is pink when alkaline and colourless when acidic. As a result of the presence of the NaCO3 the solution is alkaline at the start of the experiment. The indicator is therefore pink. As the enzyme acts the fat is broken down into fatty acids and glycerol. The solution therefore becomes more acidic and the indicator becomes colourless. The rate of enzyme action can therefore be monitored according to the speed of change in the colour of the indicator. ACCURACY The accuracy of the experiment may have been affected by the following factors: Slight variations in the concentrations and volumes of enzyme, substrate and other substances used in each of the test tubes. This would be caused by inaccurate measurements of the substances. Impurities in the solutions. Temperatures may have fluctuated in test tubes as water baths not kept at a constant temperature. To provide a more accuarate result the number of test tubes used in each temperature control could have been used. The average would then have been more reliable. More temperature controls could have been used (e.g. at 5 degree intervals). Natural lipase from the body could have been used in a separate experiment and the two experiments compared. 1 ...read more.

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