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Extracted text: Introduction: Enzymatic activity is influenced by several factors. One of these factors is the pH. The acidity and alkalinity of the substrate strongly affects the activity of enzymes. Since enzymes are mostly proteins, they react similarly to proteins and therefore are greatly dependent on pH. Generally, Enzymes are active over a small pH range and each enzyme have their own particular optimum pH. The optimum pH of an enzyme is the pH at which the enzyme has the highest activity. Below and above this optimum pH, the particular enzyme will decrease its activity. Objectives: At the end of the activity, the student can: 1. Determine the effect of acids and alkalis on reaction rate. 2. Determine the optimum pH of the enzyme used. Reagents: Saliva, 30 ml 1% starch, 1 ml 0.05N HCI, 1 ml 0.05N NAOH, 2 ml iodine in KI, 3ml benedict's reagent, 1 ml distilled water, 3 ml 0.01M NaC1 Materials: 6 Test tubes (20 ml), test tube brush, test tube holder, test tube rack, 10 ml graduated cylinder, thermometer, alcohol lamp, tripod, wire gauze, beaker, spot plate, 4 dropper, stirring rod Procedure: 1. Label 3 test tubes 1, 2 and 3. Place the substances in each test tube as indicated below: Tube 1% starch 0.1M NaC1 Acid/base/water Saliva 1 10 ml 1 ml 1ml 0.05N HC1 2 ml 10 ml 1ml 1 ml distilled H20 2 ml 3 10 ml 1 ml 1 ml 0.05N NaOH 2 ml
Extracted text: 2. Mix well by shaking each tube and place in a water bath with temperature maintained at 40°C for 30 minutes. 3. Remove all tubes from the water bath and stir. 4. Perform iodine test by taking 1 drop from each tube and place in different holes of a spot plate. Add 1 drop iodine and mix. Note color. 5. Perform benedicts test. Follow procedure as in activity 8. 6. If the result in iodine test is positive (violet to blue color) and the benedicts test is negative return the tubes in the water bath and wait for another 15 minutes. 7. Repeat procedure 4until the blue color of starch with iodine fail to appear. Note the time of the disappearance of the blue color in iodine test. 8. Then perform Benedict's test by placing 1 ml of benedicts reagent in a test tube and add 3 drops of the sample (that is already negative to iodine). Heat in a boiling water bath for 2 mins. Note color of precipitate formed. 9. If no brick red precipitate is formed, retum the tube in the water bath (40°C) for 15 minutes. 10. Repeat procedures 8-9 until a brick red precipitate is obtained. Note time of the appearance of the precipitate. Results: Tube 1 Tube 2 Tube 3 Time in Minute Iodine Benedict's Iodine Benedict's Iodine Benedict's 30 15 15 15 15 15 15 Note: Mark ( +) if the blue color appears and (-) if no blue color appears in iodine test. (+) if precipitate is formed in benedict's test. precipitate is formed and note the color of the ppt. and (-) if no