litmus paper, it turns a bluish color at a high pH and an orange color at lower pHs. Because you made your solution slig

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Litmus Paper It Turns A Bluish Color At A High Ph And An Orange Color At Lower Phs Because You Made Your Solution Slig 1 (67.12 KiB) Viewed 15 times

litmus paper, it turns a bluish color at a high pH and an orange color at lower pHs. Because you made your solution slightly alkaline in step 1. your tubes should all be about the same color- a fuchsia or magenta color. 3. Add five drops of pancreatin or pancreatic lipase solution to each test tube. 4. Add nothing to test tube 1; add five drops of vege- table oil to test tubes 2, 3, 4, and 5. Add three drope of bile solution to test tube 3. Propose a reason why you added nothing further to test tube 1. (What function is test tube 1 serving in this experiment?) 5. Place test tubes 1, 2, and 3 in the beaker serv ing as the 38°C water bath; place test tube 4 in the beaker serving as the 70°C water bath; place test tube 5 in the beaker serving as the ice-water bath. 6. Every 10 minutes for one hour, check to make: sure the temperature has not changed more than two to three degrees from the starting temperature. If it has, place the 38°C or 70°C beaker on a hot plate for a minute or two in or- der to return it to its starting temperature. The ice-water bath is unlikely to require adjustment in one hour's time, but you may add more ice if necessary. Use this 10-minute check as an op- portunity to remix the contents of the test tube by swirling or shaking the test tube from side to side. (Your instructor may demonstrate the best procedure for your test tubes.) 7. After one hour, compare the color changes, if any, that occurred in your test tubes. Use test tube 1 as your point of comparison, considering it should not have changed color during this experiment. Recalling that the enzyme should break down the vegetable oil into glycerol and fatty acids, a change in pH should occur in any tube in which the enzyme was working. Recalling that phenol red is like liquid litmus paper, a color change to pinkish-red or red is a strong positive result. A slight color change to pink would still be considered a positive reac- tion, but a weaker one. Record your results in Box 17.1. Note: It is help- ful to hold the tubes against a white background when judging your color changes. A dark back- ground makes it difficult to notice slight color changes. 8. The bicarbonate ions, which are secreted by the pancreas along with enzymes such as pancreatic lipase, raise the pH of the small intestine to ap- proximately the same alkaline range used in this experiment. However, the temperature of the hu man body in the abdominal cavity is more likely to be in the 37-38°C range. Which were the only test tubes to give significant positive reactions? Which test tube demonstrated the strongest reaction? What ingredients were initially placed in the test tube of your previous answer? Explain your results. 9. The temperatures experienced by test tubes 4 and 5 should have been too extreme for the enzyme to work. Propose a reason why it might be possible to get a alight color change in these test tubes anyway. (Hint: Review your proce- dure for this activity for potential sources of experimental error.) Bex 17.1 Results of Enzyme Activity as Measured by Color Change Test Tube 1 2 3 4 5 Color Change (Insignificant, slight, moderate, substantial)