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An investigation considering how pH affects the break down of starch by the enzyme amylase.

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An investigation considering how pH affects the break down of starch by the enzyme amylase Hypothesis: The optimum pH for the reaction of starch with amylase is pH 7. PH values lower or higher than this value will result in a slower rate of reaction. Amylase works in the range pH 3 to pH 11. Biological Knowledge PH changes affect the structure of an enzyme molecule and therefore affect its ability to bind with its substrate molecules. Changes in pH affect the ionic bonds and hydrogen bonds that hold the enzyme together, which naturally affects the rate of reaction of the enzyme with the substrate. On top if this, the hydrogen ions neutralise the negative charges of the R groups in the active site so that the substrate and the active site do not attract and therefore do not react. The optimum pH for most enzymes is pH7. In the body, amylase works mainly in the small intestines, where the acidity from the stomach has been neutralised by the hydrogencarbonate ions in the pancreatic juices secreted by the pancreas. ...read more.


It is not important whether a digital or traditional stopclock is used as there will be the same percentage error either way. Method * Measure out 1 cm� amylase solution with calibrated syringe and put in corvette * Add to this 5 drops of pH 4 buffer solution * Measure out 2 cm� starch solution * Start stopclock and leave for 1 minute * Measure out 1 cm� amylase and place in second corvette * Add to this 2 cm� distilled water * Add 3 drops of iodine solution * Shake it well, placing thumb over top * Set colorimeter to test yellow solution and % Transmission * Place second corvette in colorimeter, blank it * Once the first corvette has been left for 1 minute, add 3 drops iodine solution * Shake it well, placing thumb over top * Put in colorimeter, test * Repeat this method for pH 2, 3, 5, 6, and 7, blanking with the second corvette before each reading on the colorimeter is taken * Repeat twice so that there are 3 sets of 6 readings and calculate means ...read more.


I also initially used 8 drops of buffer solution but when I realised this volume resulted in the readings being too close to the end of the scale, I decreased it to 5 drops. When I was blanking the colorimeter before taking each reading, I initially used 3 cm� of distilled water with 3 drops of iodine. It then occurred to me that this was inaccurate, as amylase solution is cloudy. Therefore, I blanked it with 2 cm� water, 1 cm� amylase and 3 drops of iodine. I decided to experiment with pHs within the range pH 2 to pH7, as I discovered that pH 4 is the optimum pH, instead of my predicted pH7. Risk Assessment * Wear goggles to protect eyes from iodine solution * If spilt on clothes or skin, wash with water to prevent harm to the body * Keep iodine bottle away from edge of table to prevent injury from broken glassware Ethical Implications The amylase solution is taken from an animal. The owner of the animal must permit this act. The animal's body must be paid respect when the enzymes are removed so must therefore be treated carefully. ...read more.

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