Denaturation of Proteins

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Denaturation of Proteins
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What is Denaturation?

• When the unique 3-D structure of proteins is
  destroyed.
• It leads to temporary or permanent loss of
  activity.

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When and How are Proteins Denatured?

• At Very High or Low pH.
• At Very High Temperatures.
• By Heavy Metal Ions.
• By Small Polar Molecules.

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Denaturation at HIGH or LOW pH

• Affects Ionic Bonds.
• A High (gt9) or Low pH (lt3) will neutralise the
  charge on one of the ionically bonded ions.
• Hence the ionic bond is broken.

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Denaturation at High Temperatures

• As the temperature increases the energy of the
  protein increases.
• As the energy increases bonds are broken in the
  following order

• Van der Waals
• Hydrogen Bonds
• Ionic Bonds

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Denaturation by Metal Ions

• Certain metal ions will disrupt the Van der
  Waals forces in proteins.
• Heavy Metal Ions, such as Ag and Hg2, also
  inhibit enzyme activity.
• They do so by reducing the SH groups in cysteine.

PLEASE NOTE Spelling mistake on pictures ---
The S-S bond is a DISULPHIDE bond.
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Denaturation by Small Polar Molecules

• Urea ( CO(NH2)2 ) in concentrated solution will
  denature proteins.
• It disrupts the Hydrogen Bonds.
• This causes complete denaturation.

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Everyday Examples of Denaturation

• When milk curdles, the acidity increases.
• Thermal denaturation by cooking.
• Mechanical denaturation when whisking an egg.
• Perming hair breaks then reforms the disulphide
  bonds.

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• THE END
• Thank you for listening.
• This presentation, along with the one on
  Haemoglobin, will be available on my website
• www.alexridge.tk