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Lab Enzymes Activity

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The effect of different pH value on the activity of enzymes Introduction: Amylase is an enzyme which catalyses hydrolytic digestion of polysaccharides. In human's serum 8 isoenzymes of alpha-amylase can be detected. They all come from pancreas, salivary glands, mucous membrane, mammary gland, ovaries and testes. Contact of food with mucous membrane of oral cavity and even the very view or smell of food causes secretion of saliva. Saliva is produced in the amount of about 0,5 liter per 24 hours and is of pH 7,0. Solid foods in oral cavity are fragmented and mixed with saliva. Saliva contains enzyme digesting polysaccharides called 'salivary alpha - amylase (salivary amylase)'. The salivary amylase causes initial digestion of foods in the digestive system. Aim: The aim of this investigation is learning how enzyme amylase's activity and speed of digestion is influenced by different pH levels. ...read more.


Expected Results: Lugol's Iodine reacts with starch to give a dark blue color. I assume that the color in the test tubes with amylase will change and probably in the neutral pH starch will be digested best and color of the content will become transparent. Supposedly amylase in the acidic and basic solutions will digest starch poorly and solutions will not become transparent. Materials used: 1) Buffer solution at 7pH 2) 0.1 mol NaOH 3) 0.1 mol HCl 4) 1% starch solution 5) 6 test tubes 6) Test-tube holder (+ rack) 7) Distilled water 8) Solution of saliva mixed with distilled water 9) Indicator papers 10) Lugol's iodine Variables: Controlled variables: 6 test tubes are made from the same material, glass and have the same size. In 2 test tubes there is the same amount of the same solution of HCl (30 ml). ...read more.


4) To the third and fourth test tube 30 ml of HCl was added to make ph acidic. 5) To the fifth and the sixth test tubes with starch and amylase buffor was added. 6) All the test tubes were labeled. 7) Lugol's iodine was added to every test tube, to check the solution for the presence of sugar. Results: THE COLORS OF THE SOLUTIONS AFTER ADDING LUGOLA'S IODINE: NaOH Starch Amylase Brown NaOH Starch Dark blue HCl Starch Amylase Brown HCl Starch Dark blue Buffor Starch Dark blue Buffor Starch Amylase Transparent Evaluation: The results of the research followed the hypothesis. In the test tubes with no amylase reaction of starch with Lugol's Iodine occurred giving dark blue color. In test tubes with amylase digestion of starch occurred. However, differences between the speed of reaction was seen. In the test tube with buffor only (pH 7.0) a transparent solution was obtained which means total digestion of starch there. In basic and acidic solutions the color changed from dark blue which means a partial digestion. ...read more.

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