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The Effect of Pepsin on Protein

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Investigating the Effect of Pepsin on Egg Whites Medora Choi, Lily Ge Abstract: The purpose of this experiment was to investigate the effects of temperature and pH levels of pepsin on protein digestion. The independent variable was the pH level and the temperature. The dependant variable was the egg white The enzyme's action at three temperatures was tested. The effectiveness of pepsin was observed at three temperatures: 6�C (refrigerator temperature), 15�C (room temperature), and 37�C (human body temperature). Egg white was used as protein for the experiment held. This experiment lasted for 4 days. On the first day, a hardboiled egg was provided and was cut into 36 cubes using a scalpel. There were 12 test tubes, each of them containing different amounts of distilled water, pepsin, hydrochloric acid, and/or sodium bicarbonate. 3 cubes of egg white were put into one of the 12 different test tubes. Four test tubes were put in the refrigerator, another four were left at room temperature, and the last four were placed in the incubator. Over the next three days observations were recorded. Throughout the three days, the test tubes in the refrigerator and the test tubes left in the room temperature remained unchanged while the test tubes placed in the incubator dissolved. ...read more.


In test tubes 4, 8, and 12, 6 mL of distilled water was added. Each set of test tubes was then stored in different temperatures for observation. Test tubes 1-4 were stored in the refrigerator with a temperature of 6�C. Test tubes 5-8 were stored in the refrigerator with a temperature of 15�C. Lastly, Test tubes 9-12 were stored in the incubator with a temperature of 37�C. After storing the test tubes in different temperatures overnight, the first observation was made the next day. After taking out the test tubes, the observations were recorded on a table and changes of each test tube were noted. This step was repeated on the second and third day as the egg whites reacted with the pepsin. Results: Table 1 shows the observations of change relating to the twelve tubes filled with pepsin, HCI, distilled water, and/or sodium bicarbonate. Test tubes 1-4 were put in the refrigerator and there was no change from Day 1 to Day 3. Test tubes 5-8 had no change at all as well. Test tubes 9-12 dissolved the most with little of the egg white remaining. Test tubes 9-12 all looked similar to each other on all the days. All of them had a milky fluid surrounding the bits of egg whites. ...read more.


Test tubes 5-8 were left in room temperature but there was still no noticeable change in all four tubes during all the days because the temperature was not hot enough. Test tubes 9-12 were left in the incubator which was 37�C. As a result of the heat, greater action of pepsin was observed. The egg white was almost fully dissolved by Day 3 which was a great difference from the test tubes that were stored in the refrigerator and in room temperature. The temperature of the room could have affected the results of the experiment. The room temperature was supposed to be 15�C, however the room temperature was lower. This could have altered the results of test tubes 5-8 because these test tubes had very similar results to test tubes 1-4 which were stored in the refrigerator. Due to the low temperature of the room, pepsin had less action. Also, the measurement of the different liquids could have been inaccurate. The pipette couldn't have been completely exact in measurement which could have also affected the results. This was not a real error because the experiment wouldn't have been too affected by the pipette readings. However the temperature of the room could have been a problem for the experiment. Overall the results were the same as predicted, proving that the action of pepsin would be higher in a higher temperature environment. ...read more.

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