As the title suggests I am going to investigate the effect of various factors in egg white. And as all of us know that egg meals are rich in proteins and that why we feed them to small children. But not all the parts of the egg have the same amount of proteins in them and as we know that there is the yellow part which has fairly less amount of protein compared to the white part and that is why I chose the white part to test the effect various external factors on the protein which it contains and it is called albumen. And to understand what I am going to do in my coursework I am going first to give a small explanation on the nature of the proteins and their structure in general and albumen in special.
Proteins are in general made of small particles called amino acids. And this is achieved by when many amino acids combine together to form polypeptides in a condensation reaction. Those polypeptides join together also by a condensation reaction to form a protein. And this is in short how albumen is also formed. And thus we could say that amino acids are the basic units from which proteins are formed of and below is a structure of an amino acid.
N C C
H H OH
As we see above this is a simplified structure of an amino acid and from the diagram we could see that structure has in its center a carbon atom which is called the alpha carbon and to this alpha carbon there are four different groups attached to it and they are as follow. The first one is a hydrogen atom the second is a basic amino group and the third is the carboxyl group (COOH) which is usually acidic in most cases and in the end the fourth group is the ‘R’ group which is variable in length and plays an important role in determining and deciding the nature of the amino acid. Therefore any amino acid, which has in its place a carboxyl group, which is an additional one would be an acidic one and if in its place it has an additional amino group it, would be a basic.
That was in summary a brief explanation of the structure of an amino acid but for each structure should be held by bonds which keep them in shape and in my experiment I am going investigate how the effect various factors like acids and alkalis have on maintaining those bonds and that why we should take a look on the bonds holding the structure of amino acids. The bonds holding the amino acids are hydrogen bonds, which are founded between CO and NH groups. The second type is the ionic bonds, which occurs when the ‘R’ group exits in an ionic form. The third type is the disulphide bond, which occurs between the sulphur groups of the amino acid cytosine. The last type is the hydrophobic bond and which is the most important in maintaining the structure of a protein and that is because the exclude water molecules in an aqueous environment. Moreover there are two types of proteins one is the fibrous proteins and the other is the globular proteins which albumen belong to this group and the most important characteristics of this group are that they are soluble in water and its chains are folded to form spherical shapes as shown below.
Now any change in the structure due to any external factors, which affect the protein, will cause a change in its shape leading the protein not to carry its proper function. This process is called denaturation. When this process occurs in the protein albumen the albumen reverse to become a fibrous protein causing a white insoluble curd to form called the coagulation of the albumen.
For denaturation to occur there are several factors which helps it to happen and this what I am going to investigate. One of those factors and which we know since lower classes is heating. Heating causes the atoms within the protein to gain kinetic energy and breaking the bonds. Other factors are like adding acids, alkalis, heavy metals etc.. . Those chemicals combine with the COO groups in the protein leading to a change in the structure and the denaturation of the protein. Those chemicals also form coagulated albumen when added to albumen.
After going through what I wrote above I came to a personal conclusion which I am going to make it as my hypothesis is that the amount of coagulated protein formed increases or proportional to the concentration of the chemicals used which are external factors and physical factors it was exposed to.
Now after mentioning my hypothesis I am going now to test the truthfulness of this hypothesis I am going to carry out an experiment to prove it and below is how I am going to plan my experiment and what chemicals I am going to use and etc.. .
And below is a graph, which shows what I mean:
At the beginning when I decided to start my experiment I decided to investigate a physical factor along with using chemicals. And the physical factor I decided upon was freezing that is because we know the effect of heating so I was interested to observe what freezing would do to egg albumen. This was for the physical factor, for the chemicals I decided to observe the effect o f acids, alkalis and heavy metals and for the acids I decided to use hydrochloric acid (HCl) and for the alkali I decided to use sodium hydroxide (NaOH) and for the heavy metals I decided to use either mercury chloride or silver chloride depending on the availability. And for each chemical I decided to use three different concentrations for each and they are going to be .0.25M, 0.5M, 0.75M and 1M for the acid, alkali and the heavy metal.
To carry out the experiment I got to use some materials and apparatus and below is a list of them followed by the use of each in brief:
* Test tubes
* Measuring cylinders (10 cm, 5 cm)
* Test tube holders
* Lab stickers
* Glass rod
* Hydrochloric acid
* Sodium hydroxide
* Silver chloride
Each of the materials and apparatus above has specific uses as shown below:
Beakers: are going to hold the whole amount of the egg white and acids, alkalis and the heavy metals.
Test tubes: are going to be used to pour the contents together in it for the reaction
to take place.
Measuring cylinders: are going to be used to measure the contents of the chemicals I am going to use.
Droppers: these are going to be used to adjust small amounts when I pour the chemicals in the measuring cylinders like taking on ml off.
Test tube holders: are going to hold the test tubes used for the reaction.
Lab stickers: are going to be used to label the test tubes to know which is which.
Glass rod: are going to be used to stir the contents of the test tubes and skim off the amount of coagulated protein formed.
Freezer: is going to be used to place in it the test tube, which is going to test the effect of freezing on egg albumen.
Eggs: are of course going to be used to get from them the egg white or egg albumen for the experiment.
Hydrochloric acid: it is what I chose from all the ranges of acids to test the effect of acid on egg albumen.
Sodium hydroxide: it is what I chose from all the ranges of alkalis to test the effect of alkali on egg albumen.
Silver chloride: it is the heavy metal, which I choose to test the effect of heavy metals on egg albumen.
And that was in brief the use of each material and the purpose for what I am going to use them.
The experimental procedure to be carried:
Now I am going to explain how I am going to carry out my experiment. First of all I will get some eggs, separate the egg white from the yellow part of it, and pour them in a beaker. Then I am going to get 30 cm of the acid for each concentration and pour them in four different beakers, which means that for 1 M I will get 30 cm of it in a beaker and the same for the other three concentrations. I will then repeat the same procedure for the sodium hydroxide and the silver chloride. Then I will take a measuring cylinder and pour in it 10 cm of egg white in it. Then I will take the acid and pour in it in another measuring cylinder also 10 cm of it. After that I take the egg white, pour it in a test tube and above it the acid, and wait until the reaction finishes. The time for which the reaction to finish will depend on how many days would I leave it there fore I decided to leave the mixture of acid and egg white for four days to give it the maximum time for it to finish its reaction. After that I will measure the volume of coagulation formed for example if the coagulation formed was the full 20 cm then I am going to give it a symbol which will be 5 and so on depending on the volume formed. This procedure, which I used for the acid, is going to be the same for the sodium hydroxide and the heavy metal used thus guarantying a fair test.
Precautions to be taken:
When carrying the experiment one should be careful and below is the list of the precautions I took:
* Wearing gloves: this important because it would protect my hands in case the acid, alkali and the heavy metal I am going to use can fall on the and burn my hands.
* Lab coat: same as above but for the protection of the rest of my body.
* Not breaking glass apparatus: so as not injure my hands by glass shards caused by the breaking of the glass thus I should be careful.
* Electric points: as I am going to test the effect of freezing it would be normally that I am going to use a freezer that is why I got to check the electric points so as not to get an electric shock
* Eye protection: I am going to wear eye goggles to protect my eyes in case a splash of acid reaches my eyes.
* Protection against salmonella: as all of us know that the surface of the egg, which means the eggshell, contains the bacteria salmonella thus one should
Take care to wipe the eggshell first before the experiment and to wash his hands thoroughly after finishing his experiment.
Factors to be controlled:
For a fair test to be carried there are various factors to be controlled to ensure that fair test to be carried and below are the list of factors that should be controlled:
* Maintaining a constant temperature: to make sure that the experiment goes smoothly one should maintain a constant temperature preferably a room temperature and that is because it the temperature was raised the rate of reaction will change.
* To leave all the test tubes for the same time so as none of them will have an advantage on the other.
* Same amount of egg white to be used in all as the same amount of acid, alkali and heavy metal to be same through out the whole experiment.
* To ensure accuracy one should repeat each experiment at least twice and take the mean of the values recorded.
* I will try to make the reaction go by itself and prevent shaking any of the test tubes to give a fair chance to all the other test tubes.
After carrying on the experiment I am going to record my results in a table, which is shown on the next page: