2 add 05 ml of water to tube 1 and 05 ml of 1 trypsin

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2. Add 0.5 ml of water to tube 1 and 0.5 ml of 1% trypsin solution to tube 2 . 3. Mix well and place both tubes in the 37 o C water bath for 30 minutes. 4. Place both tubes on ice for 15 minutes and then let them gradually warm up at room temperature. 5. Invert each tube periodically to see which tube liquefies first and record on your worksheet.
92 Digestion of Starch by the Enzyme Amylase Starch is a large polymer of the monosaccharide glucose. In order for your body to obtain glucose from the starch you eat, it must be digested by the enzyme amylase : Amylase is present in human saliva as well as pancreatic juice. The amylase you will be using is produced by a fungus. As you learned in the previous lab, starch can be detected by the addition of a small amount of iodine solution. If starch is present the sample will turn dark blue or black when iodine solution is added, if there is no starch then the sample should be a clear light brown color. The complete digestion of starch to free glucose should thus result in a clear light brown color when iodine solution is added. Partial digestion of starch will result in a color that is somewhat dark but not as dark as an undigested starch sample. In the next exercise, you will use iodine solution to determine if starch is digested by amylase. Exercise 3 – Digestion of starch by amylase In this exercise you will set up three reaction tubes. Two reactions will serve as controls, one lacking the enzyme and the other lacking starch. The third reaction will contain both the enzyme amylase and its substrate, starch. Your three reactions should be performed as follows: 1. Label three test tubes 1 , 2 & 3 and add the indicated components in the order listed. Tube 1 Tube 2 Tube 3 starch solution 2.5 ml none 2.5 ml water 0.5 ml 2.5 ml none 1% amylase none 0.5 ml 0.5 ml TOTAL 3.0 ml 3.0 ml 3.0 ml 2. Mix well and incubate each tube at room temperature for 10 minutes. 3. Add 3 drops of iodine to each tube, mix and record the results on your worksheet. ( Record the color immediately after mixing since it may fade ) NOTE: Save your control tubes (tubes 1 & 2) from Exercise 3 for use in Exercise 4.
93 Effect of pH on Enzyme Function As you learned earlier, enzymes are proteins and proteins only function properly in their native conformation or shape. If anything causes an enzyme to lose is shape, i.e., to become denatured , it will no longer function as a catalyst since it can no longer bind to its substrate. Changes in temperature, pH and salt concentration all can denature an enzyme and destroy its activity. To illustrate this, you will design an experiment to test the effects of changes in pH on the activity of the enzyme you used in the previous exercise – amylase. Human pancreatic enzymes such as lipase, trypsin and amylase normally carry out their catalytic activities at relatively neutral pH values of 7 to 8 in the small intestine. Fungi digest food sources containing starch externally in slightly acidic environments close to pH 5. You will be using fungal amylase for following experiments , so keep this in mind when you come up with your hypothesis .

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