Denaturation of Proteins
What is Denaturation?
 When
the unique 3-D structure of proteins
is destroyed.
 It
leads to temporary or permanent loss of
activity.
When and How are Proteins
Denatured?
 At
Very High or Low pH.
 At
Very High Temperatures.
 By
Heavy Metal Ions.
 By
Small Polar Molecules.
Denaturation at HIGH or LOW pH
 Affects
Ionic Bonds.
 A High
(>9) or Low pH (<3) will neutralise
the charge on one of the ionically bonded
ions.
 Hence
the ionic bond is broken.
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 Waal’s
• Hydrogen Bonds
• Ionic Bonds
Denaturation by Metal Ions
 Certain
metal ions will disrupt the Van der
Waals’ forces in proteins.
Metal Ions, such as Ag+ and Hg2+,
also inhibit enzyme activity.
 Heavy
 They
do so by reducing the SH groups in
cysteine.
PLEASE NOTE: Spelling mistake on
pictures: --- The S-S bond is a
DISULPHIDE bond.
Denaturation by Small Polar
Molecules
 Urea
( CO(NH2)2 ) in concentrated solution
will denature proteins.
 It
disrupts the Hydrogen Bonds.
 This
causes complete denaturation.
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.
THE END
Thank you for listening.
This presentation, along with the one on
Haemoglobin, will be available on my website:
www.alexridge.tk