protein denaturation experiment lab report

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Lab 10, Denaturing Proteins

Ess of org chem-lab (chem 121.lb), hunter college cuny.

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Mohammed Abdelrehem May 7, 2019 Professor Zdarvkovic CHEM 121 Precipitating & Denaturing Proteins Lab Report Purpose: The purpose of this lab is to observe how the protein, albumen in egg whites, reacts in different conditions such as: high pH or low pH, neutral environment, high temperature, and ionic environments which may cause the protein to denature and/ or precipitate. Chemicals & Equipment:  Egg whites, hot plate, beakers, test tubes, stopper, universal pH paper  3 M HCl, 3 M NaOH, acetone, solid NaCl, 0 M Cu2+, 10% tannic acid, 0 M Pb2+ Summary Procedure:

Using a beaker pour in about 30 mL of egg whites and 70 mL of water. Continue to swirl the water and the egg whites in the beaker to make it more homogenous. In 10 test tubes put 3 mL in each test tube. Pour gently in. For the first test tube heat it in the beaker with hot water on the hot plate and observe any changes. For the second test tube add a cork stopper on the top of the test tube and shake it vigorously for 20 seconds and observe any change. For the third test tube add about 1 mL of 3 M HCl if there is precipitation then measure the pH of the solution and then add 3 M NaOH roughly the same amount of HCl with mixing, measure the pH and continue adding NaOH until it is slightly basic or neutral. For the fourth test tube add about 1. mL of 3 M NaOH if there is precipitation then measure the pH of the solution and then add 3 M HCl roughly the same amount of NaOH with mixing, measure the pH and continue adding HCl

until it is slightly acidic or neutral. In the fifth test tube add 0 g at a time of solid NaCl and mix it until the solution is saturated. To the sixth tube, add 10 drops of 0 M Cu (NO3)2 dropwise with gently mixing. To the seventh tube, add 10 drops of 0 M Pb (OAc)2 dropwise with gently mixing. To the eighth tube, add 10 drops of 10% tannic acid dropwise with gently mixing. To the ninth tube, add acetone dropwise until the volume increases by 50% or no there is no more protein present. Observe and record any changes that can be seen.

Data/Results:

Test tubes Observations Denatured/Not Denatured 1- Boiling water White solid formed & solution turned white

2- Shaking vigorously became white & bubbly Denatured 3- HCl 3M became white, precipitate formed, had a pH of 0, after NaOH was added there was a pH of 8 and more precipitate formed

4- NaOH 3M no visible reaction, pH 13 Not denatured 5- Solid NaCl (.5 grams) NaCl solid dissolved in egg white solution completely

Not denatured

that the proteins were denatured. I don’t think it is possible for a protein to precipitate, yet not denature.