Denaturation of Proteins --- Mini Worksheet
1) What is denaturation (in terms of proteins)?
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2) Why is it important to living organisms that their proteins are not denatured?
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3) Name three ways in which a protein can be denatured. For each one give the
conditions.
Example
What is affected
Conditions
Hydrogen Bonds
Small polar molecule (eg Urea)
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4) (SAQ 2.17, a)
Increasing the Temperature causes molecules to vibrate more quickly. Explain
how this can cause protein denaturation.
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5) (SAQ 2.17, b)
Extremes of pH will cause many of the R groups of the amino acid residues
along a polypeptide chain to gain or lose an H+ ion. Explain how this can break up
both secondary and tertiary structure.
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6) Hair is made of an insoluble fibrous protein. The shape of hair can be changed in a
way that lasts for some time by changing the disulphide (–S–S–) bridges present.
Small sulphur-containing molecules such as thioglycollate can bring this about.
Hairdressers first use rollers to create a new style for the hair. They then apply
the thioglycollate solution to break apart the disulphide bonds, producing –SH groups.
This allows the protein chains to re-arrange themselves to the new shape of the hair.
The thioglycollate is thoroughly washed away. The hair is fixed in its new shape
(made permanent or ‘permed’) using a dilute hydrogen peroxide solution which reforms new disulphide bridges.
a) Which insoluble fibrous protein in hair made of?
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b) Are the disulphide bonds mainly responsible for the secondary, tertiary, or
quaternary structure of the proteins?
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c) Which types of reaction are carried out by
i. The thioglycollate solution
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ii. The hydrogen peroxide
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d) What causes the shaping of the hair to eventually be lost, and why?
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