Effect Of Ph On Enzyme

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Investigating ‘The Effect of pH on Enzyme Activity’ Introduction: Enzymes are very sensitive to pH changes. Most enzymes work best at a pH of 7, but this is not always the case, for example, enzymes in the stomach work best ‘optimally’ at very low pHs. The pH at which an enzyme works best is described as its ‘optimum pH.’ At pHs far form the optimum pH, the enzyme can become denatured. Aim of practical: To find out the effect of pH on an enzyme reaction. Plan: Amylase is an enzyme that breaks down starch to a sugar (maltose). -Label 5 test tubes 1-5. -Place 5cm3 of starch solution into each test tube. -Add 2cm3 of pH solution to each test tube. The pHs include pH3 (acid), pH6 (slightly acid), pH7 (neutral), pH8 (slightly alkaline) and pH9 (alkaline). -Place 1cm3of amylase enzyme into each test tube. Shake the tubes gently and immediately start stopclock. -Every minute remove a sample and test with one/two drops of iodine solution. -Continue until iodine stays brown. Record time for the starch to be broken down in seconds in the table below. Results Table: pH | Time taken for starch to be broken down by amylase (in seconds) | 3 (acid) | 900 | 5 (slightly acid) | 600 | 7 (neutral) | 240 | 8 (slightly alkaline) | 360 | 9 (alkaline) | | Questions a) Plot a graph of pH on the x-axis and time taken for starch to be broken down (in seconds) on the y-axis. b) At what pH did the enzyme, amylase, work most rapidly? Explain * The amylase worked most rapidly at pH7. This is because the Starch enzyme would work best at ph7 as that is our body’s standard pH. c) Your stomach pH is about 2. Would you expect starch digestion to take place in the stomach? * I would not expect Starch digesting to take place in the stomach and it would take a lot of time to

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