Discovering Factors affecting Protein Denaturation

Essay by PardeepkHigh School, 12th gradeA, February 2010

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To examine three different ways of denaturing proteins.

HypothesisIt was predicted that the physical characteristics of the egg white solution at room temperature would appear clear and normal like a raw egg white. This is because nothing would be done to the egg white. It was also predicted that when the egg white solution gets heated, the protein would denature if the temperature exceeds 65 °C. The protein would solidify, turn opaque, and turn white in colour. This would happen because the heat at a certain temperature will cause the amino acids in the protein to unravel, thus the protein would lose its structure, and this would reveal a colour change. It was also predicted that when acid is poured into the egg white solution, the proteins would denature and turn into a white colour. This would be because it would result in a further straightening effect on the protein chain.

It was also predicted that when silver nitrate is poured into the egg white solution, it would result in some sort of precipitate since silver is always precipitating out. Also, since salts are ionic compounds, they disrupt salt bridges in proteins, and so this can also be a factor.

It was hypothesized that egg whites will not regain their original characteristics when removed from the heat or acid because if the protein bonds get disrupted, then the protein is no longer viable and cannot perform its function when it is partially or fully uncoiled.

ObservationsTable 1: Chart illustrating the pH and appearance of the egg white solution in test tube A at room temperature (25 °C).

Test TubeTemperaturePHAppearanceA25 °C8 - BasicClear solution with foam at the top. Contained tiny white particles floating in the egg white.

Table 2: Chart illustrating the pH and appearance of the egg white solution in test tube B when heated in boiling water for ten minutes.

Test TubeAppearanceBOpaque solution. Cloudy, foamy at the top. Had a creamy colour.

Table 3: Chart illustrating the pH and appearance of the egg white solution in test tube C that contained 1M Hydrochloric acid (2.00 mL).

Test TubePHAppearanceC2 - Acidic Opalescent solution. Fewer amount of white particles floating in solution. Foam at the top of solution.

Table 4: Chart illustrating the pH and appearance of the egg white solution in test tube D containing Silver nitrate (5 drops). In total, seven drops of Silver nitrate was poured into the solution.

Test TubeAppearanceDOpaque solution. Foam at the top of solution. Creamy colour.

Figure 1: Illustration showing the egg white solution in all of the three test tubes being conducted on.

Discussion1. What was the purpose of tube A?The purpose of tube A was to have it as the control variable in the experiment. The quantity of the solution in test tube A was to remain constant throughout the experiment.

2. What common result occurred in all three tubes?The common result that occurred for all three test tubes was that the albumen solution had turned white. This was because test tubes B, C, and D all encountered protein denaturation because the structure of the protein broke down, so new bonds were formed between the amino acids, which resulted in the texture change. Adding on, the loss of biological activity had also occurred in all three test tubes, meaning that the ability to act as enzymes or hormones was lost.

3. What three factors have caused denaturation in this experiment?The three factors that have caused denaturation were: heat, acid, and salt.

Questions1. The albumin part of an egg white consists of a simple protein. Heavy metal salts will combine with the proteins, and when this occurs, they are harder to absorb. Therefore, the egg white may slow or limit the absorption of the heavy metal toxins. To add on, protein is very good because the sulphur-bearing amino acids in the protein will significantly facilitate detoxification.

2. The egg yolk contains a lot of fat and other stuff. This might prolong the protein denaturation in the egg yolk. Further more, there is more fat in the egg yolk to protect the proteins. Also, different parts of the egg contain very different substances, and this can also be a factor. To add on, another reason could be that the cooking heat must penetrate the egg white in order to reach the yolk.

3. When one has a high fever, proteins are denatured because of high temperatures. In some cases, having a high fever for some time can lead to brain damage, and this can be due to the denaturing of proteins at high temperatures. One method of treating high fever would be using egg whites and placing them on the soles of your feet. This bringsthe temperature down from the brain to the feet. Another important way of treating high fever is to take a cool bath and placing a cool towel on your forehead. This would be very useful because it would lower the body’s temperature and stop protein denaturation to occur.

4. Foods and vegetables are blanched using a simple method. Fruits and vegetables are plunged into the boiling water for a minute or so, and then heat is removed. The fruits and vegetables are drained. Afterwards, the fruits and vegetables are plunged into very cold water. The step of boiling the fruits and vegetables and placing them in cold water should be done immediately.

5. Blanching does a few things to the fruits and vegetables. Firstly, the hot water destroys the enzymes contained in the fruits/vegetables. To add on, blanching also kills microbes and insects as well as eggs that exist in the fruits/veggies. The cold water stops it from cooking. Blanching is also used to preserve the freshness and natural color of the fruits/veggies as it can prevent discoloration and enhance the existing color.

6. A food company would blanch certain fruits/veggies before packaging them in a transparent jar for a few reasons. Firstly, blanching would prolong shelf life and would be better for the consumer. It also makes the fruit/veggie look fresh and have a rich colour to it. This would make consumers buy the product because of its fresh appearance.