Concentrations Of 0 1 example essay topic

Aim To find out the lowest concentration of copper (II) sulphate solution that brings about full denaturation of egg albumen. Background Information Denaturation is the breakdown of the bonds forming the quaternary, tertiary and secondary structures of proteins and nucleic acids. Changes in the shape of a protein lead to its inactivation. Albumen is a globular protein, which contains carbon, oxygen, nitrogen and hydrogen. Proteins usually contain sulphur too. Globular proteins are composed of a rounded, compact mass of an intertwined protein chain. the precise shape of the globular form is due to the interrelations of the component amino acids as they seek the lowest free energy state for the protein.

Once the lowest free energy state for a particular protein has been achieved, it is said to be in its native or functional state. Only when in its native, or low energy, state does a protein manifest all of its characteristic properties and biological functions. The denaturing of a protein occurs when the protein chain unfolds and when this happens the protein no longer retains its biological functions. 'Denaturation does not involve splitting amino acids from the polypeptide chains. ' This, therefore, means that a denatured protein can return to its original state and resume its specific 200 biological activity. Denaturation / denaturation of a globular protein (Lehninger 1970) The egg albumen is held together by interactions between the R groups.

Some of theses R groups are ionic and a positively charged R groups are attracted to negatively charged R groups. It's force of the attraction holds together the shape of the protein. Copper sulphate dissociates into Cu 2+ and SO 42- ions. The Cu 2+ ions are attracted to the positively charged R groups and the SO 42- ions are attracted to the negatively charged R groups.

This causes the charge on the R groups to neutralise so that they no longer bind to each other and therefore the protein uncoils into long strands. Preliminary Experiments I decided to carry out the experiment by mixing 5 cm^3 of the albumen with 5 cm^3 of different concentrations of copper (II) sulphate solution. I used concentrations of 0.1, 0.08, 0.06, 0.04, 0.02 and 0.00 mol dm-3. I then decided to use a colorimeter to find out how opaque the mixture containing the concentration of 0.06 mol dm-3 of copper sulphate solution was. It gave me a reading of 1 arbitrary unit which indicated to me that the mixture was completely opaque. This told me that the concentrations I had chosen to use were too high.

400 While I was using the colorimeter I realised that the precipitate distributes itself unevenly in the solution. This means that different amounts of light will get through different parts of the mixture and so this piece of equipment will not give an accurate reading. Safety Precautions 1. Wear safety goggles, overall and gloves as copper (II) sulphate solution can damage skin and eyes. Prediction After carrying out my preliminary experiments I found that the concentrations I was using were too high and so I am going to use lower concentrations of the copper (II) sulphate solution. I think that the lowest concentration of copper (II) sulphate solution possible to denature albumen will be 0.035 mol dm-3.

Apparatus. White piece of paper with a dark cross on it. Measuring cylinder (100 cm^3). Glass rod.

5 boiling tubes. Test tube rack. 2 syringes (5 cm^3). Beaker Substances needed. Copper sulphate (II) solution. Egg albumen.

Distilled water Key Variables Controlled variables: -. Volume of egg albumen in each boiling tube. Volume of copper (II) sulphate solution in each boiling tube Independent variable: -. Concentration of the copper (II) sulphate solution Method 1. Measure 5 cm^3 of albumen in a measuring cylinder (100 cm^3) and pour it into a boiling tube. Add 5 cm^3 of distilled water to it and stir with a glass rod.

This boiling tube will be used as a control to see what the egg albumen looks like when it is not denatured. 600 2. 3. Using syringes measure 2.5 cm^3 of distilled water and 2.5 cm^3 of copper (II) sulphate solution into a beaker. (This will give the copper sulphate (II) solution a concentration of 0.05 mol dm-3) 4.

Pour the copper sulphate (II) solution into the albumen and stir with a glass rod. 5. Place the paper with the cross on it directly behind the boiling tube and if you can still see the cross then the albumen will not have been fully denatured. 6.

Repeat steps 1 to 4 using concentrations 0.04, 0.03, 0.02 and 0.01 mol dm-3.7. If a result is found to be in between 2 of the concentrations, e.g. the cross disappears at 0.04 mol dm-3 but not at 0.03 mol dm-3 then make the concentrations even more precise. For this particular example a concentration of 0.035 mol dm-3 could be used. 8.

Repeat until the lowest concentration of copper (II) sulphate solution is found that will fully denature albumen i.e. it will become fully opaque. 9. When the lowest concentration has been found repeat the whole investigation 2 more times. 800 Precision This method is a relatively accurate method to carry out this investigation.

The syringe used to measure out the copper (II) sulphate solution is highly accurate and by doing repeats an average concentration can be calculated so that the results are as accurate as possible. To improve the method further the substances could be put in a water bath so that a constant temperature is maintained throughout the whole experiment. During the experiment the results can be recorded in a table. When the investigation is complete and all the results have been collected the data could be represented on a graph. Here is an example of what the graph may look like. Reference List.

Collins Dictionary of Biology - WG Hale, JP Markham, VA Saunders (1988). web. web. Introducing Biochemistry - E.J. Wood, W.R. Pickering (1982). Biochemistry - Lehninger (1970). Biochemistry - Martin Carr, Bob Cordell (1992).