Biology Experiment- Enzymes

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Investigating the effect of pH on amylase activity This practical allows you to: • discover how pH affects the rate of an enzyme controlled reaction • evaluate the experimental procedure Procedure SAFETY: Follow your teacher’s instructions for handling the solutions. Wear eye protection when handling the iodine solution. Investigation a Place single drops of iodine solution in rows on the tile. b Label a test tube with the pH to be tested. c Use the syringe to place 2 cm3 of amylase into the test tube. d Add 1 cm3 of buffer solution to the test tube using a syringe. e Use another syringe to add 2 cm3 of starch to the amylase/ buffer solution. Start the stop clock and leave it on throughout the test. Mix using a plastic pipette. f After 10 seconds, use the plastic pipette to place one drop of the mixture on the first drop of iodine. The iodine solution should turn blue-black. Squirt the rest of the solution in the pipette back into the test tube. g Wait another 10 seconds. Then remove a second drop of the mixture to add to the next drop of iodine. h Repeat step g until the iodine solution and the amylase/ buffer/ starch mixture remain orange. i You could prepare a control drop for comparison with the test drops. What should this contain? j Count up how many iodine drops you have used, each one equals 10 seconds of reaction time. k Repeat the whole procedure with another of the pH buffers or pool your results with others in your class. l Collect repeat data if there is time. m Plot a graph of time taken for starch to break down against pH. OR Calculate the rate of the reaction by calculating 1 ÷ time. Plot rate of reaction against

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