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Denaturing Proteins

based on 57 ratings
Author: Cy Ashley Webb

Grade Level: High School; Type: Biochemistry

Objective:

The objective of this experiment is to determine whether all proteins denature at the same temperature.

Research Question:

  • What happens when a protein denatures?
  • Do all proteins denature at the same temperature?
  • What temperature does albumen denature at?
  • What temperature does keratin denature at?
  • What temperature does casein denature at?
  • Why might proteins denature at different temperatures?

Denaturation is a process in which proteins lose their structure when attacked by forces like a strong acid, heat, or a solvent like alcohol. If a protein is denatured, it can die. In this experiment, you will determine the temperature that will denature proteins like albumen, casein, and keratin. Eggs are mostly albumen, milk is largely casein, and hair is mostly keratin.

Materials:

  • Small saucepan
  • 6 eggs (any size)
  • 2 mixing bowl
  • Candy thermometer
  • Powered Milk
  • Cookie Sheet
  • Aluminium foil
  • Hair from a hairbrush
  • Comb
  • Toaster oven (or conventional oven)

Experimental Procedure

  1. Crack an egg over the first bowl and separate the yolk and white. Use two bowls, keeping all the whites in one of the bowls. Make sure that your yolks do not contaminate the whites.
  2. Transfer the whites into a small saucepan. Place the candy thermometer into the saucepan.
  3. Gently heat the whites. Record the temperature when their texture changes.
  4. Clean the saucepan, thermometer, and bowls.
  5. Make two cups of reconstituted powdered milk according to the package directions and add to the saucepan. Place the candy thermometer in the saucepan.
  6. Gently heat the milk. Record what temperature the texture of the milk changes or a skim forms over the top.
  7. Cover a cookie sheet with aluminum foil.
  8. Preheat the oven for ten minutes to 200 degrees.
  9. Using a comb, pull all the hair out of a hairbrush and put on the cookie sheet.
  10. Put the cookie sheet and hair into the oven. Let it heat up for 15 minutes. Inspect the hair for any changes.
  11. Increase the temperature by 25 degrees. After 15 minutes, inspect the hair again.
  12. Keep increasing the temperature in 25-degree increments. Note when the hair texture changes.

Terms/Concepts: protein, amino acid, denaturation

References:

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