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Orientation:
This activity is designed to illustrate the denaturation of protein (by heating). Study the instructions below. In your activity journal, answer the questions that follow each description.
Supplies:

Access the Student Journal for Activity 2
eggs
dishes to separate the whites into
source of heat sufficient to cook egg white
glasses of water


Activity 2: The Denaturation of Proteins

Have you ever had to separate the yolk of an egg from the egg white for a recipe? Egg white consists mostly of a protein called albumin. In this experiment, you will test how denaturation of a protein (albumin from egg white) affects the protein's solubility (ability to dissolve) in water.


Egg Yolk Image
1. Carefully break an egg and pour out the white part into a dish, leaving the yellow yolk part behind. Be careful not to break the yolk. Do not get any egg yolk in dish.

2. Take a small fraction of the egg white and put it in a glass of water. What happens? Does it dissolve?

Boiled Egg Image3. Heat the egg white, which is mostly albumin protein, until it cooks. How does the appearance change?

4. Cut a small piece of the cooked egg white and put it in the same volume of water that you used in step 2 above. Does it dissolve?

Interpretation: Why does heating cause a change in appearance? Why does heated egg white not dissolve? When you fry an egg, why does the white congeal first before the yolk? All of these questions can be answered by thinking about the hydrogen-bond basis for coiling and folding of proteins.

 

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