Protein Structure: Effect of pH and Temperature

The 3D conformation of proteins is stabilised by weak hydrogen bonds or interactions between R groups of amino acids

The bonds are easily broken by heat or changes in pH

The denaturation is permanent, often forming an insoluble precipitate

Heat

Increases kinetic energy causing vibrations within molecules

Breaks the weak bond or other interactions within the molecule

The polypeptide chains will unfold causing the overall 3D shape to change

pH

If the pH is increased by adding an alkali or decreased by adding acid changes the attractions between the groups in the side chains of the polypeptide

These attractions are important for the 3D shape of a proteins

The disruption compromises the functionality of the protein

Denaturation of albumen in egg white by heat

When an egg is fried, the added heat leads to breakage of hydrogen bonds and cross-linkage between sulfur containing R-groups of amino acids in the polypeptide forming disulfide bridges

Water is trapped inside this structure, making it form an insoluble soft gel