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Denaturing Proteins

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michele wiebe

on 4 December 2013

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Transcript of Denaturing Proteins

Denaturing Proteins
Biology 11
Michele Wiebe and Delillah Meservy
December 1, 2013

Small saucepan
6 eggs (any size)
2 mixing bowl
Candy thermometer
Powered Milk
Cookie Sheet
Aluminium foil
Hair from a hairbrush
Toaster oven (or conventional oven)
1. Crack an egg over the first bowl and separate the yolk and white.
2. Use two bowls, keeping all the whites in one of the bowls. Make sure
that your yolks do not contaminate the whites.
3. Transfer the whites into a small saucepan. Place the candy thermometer
4. Gently heat the whites. Record the temperature when their texture changes.
into the saucepan.
5. Clean the saucepan, thermometer, and bowls.
6. Make two cups of reconstituted powdered milk according to the package
directions and add to the saucepan. Place the candy thermometer in the
7. Gently heat the milk. Record what temperature the texture of the milk changes
or a skim forms over the top.
8. Cover a cookie sheet with aluminum foil.
9. Preheat the oven for ten minutes to 200 degrees.
10.Using a comb, pull all the hair out of a hairbrush and put on the cookie sheet.
11. Put the cookie sheet and hair into the oven. Let it heat up for 15 minutes.
Inspect the hair for any changes.
12. Increase the temperature by 25 degrees. After 15 minutes, inspect the
hair again. Keep increasing the temperature in 25-degree increments.
Note when the hair texture changes.
When we test to see what temperatures Albumen (egg), casein (milk) and keratin (hair) denature at, we believe they will happen at different temperatures. We think that Albumen will denature first and Keratin will be the last to denature.
Delillah and Michele will be conducting the experiment in Michele's kitchen.
We wanted to do this experiment because proteins are so important for everyone. Everyone needs them and we thought it would be good if we learned more about proteins and how they work.
Denaturation is a process in which proteins lose their structure when attacked by forces that break their Hydrogen-bonds. Heat can do this at the right temperature.
My dependent variables are the proteins that we used. The egg, hair, and milk were all manipulated by us. we tested them with heat to denature them. The heat killed their function.
Independent variable
The independent variables were the heat that we used. The heat changed the proteins but the proteins did not change the heat.
Our proteins will be
albumen (egg)
casein (milk)
keratin (hair)
(degrees Fahrenheit)
Our data wasn't really what we were expecting. We didn't think that our hair sample would be able to be at the temperature it was at for so long. Our hair was in the oven for over half an hour. When the hair came out, we saw that it was very brittle and very easy to break in half. The hair was very dry and had a wire kind of texture to it.
Our egg on the other hand was what we were expecting. When we cook eggs, the temperature doesn't have to be very high and the egg still cooks quite fast. For our experiment, we noticed that the egg only had to be in the heat for 5-8 minutes before the proteins started changing. The egg turned into a solid.
The milk we weren't really sure what was going to happen. Delillah thought that it also wouldn't take too long for something to happen but we ended up waiting between 10-15 minutes for the milk to change. It also ended up turning into a foamy liquid
Some improvements we could do if we were to retry our experiment would be to make sure that you use the same amount of material for every trial. Make sure to measure how much of everything you used because if you used only a tiny bit of egg or milk, the proteins would denature faster then if there was a lot of milk or egg. Next time we could also just focus on one protein and see if acids, alcohol and bases would affect that certain protein.
We believed that the proteins would denature at different temperatures and we were right. We also believed that the hair protein would denature last and the the egg would denature first. That also worked out like we thought it would.

We learned that just as everyone is different, so are proteins. Since different proteins have different structures, it will be harder to denature certain ones. Proteins need to suit their environment. For example, keratin needs to be able to denature at a higher temperature because its found in our hair and if it denatured in low temperatures, then it wouldn't be able to protect our head as well.
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