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. • 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.
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