Define the following terms as related to proteins:

(i) Peptide linkage
(ii) Primary structure
(iii) Denaturation

(i) Peptide linkage: It is the amide formed between the −COOH and −NH₂ groups of two amino acid molecules.

(ii) Primary structure of proteins: Proteins contain one or more polypeptide chains and each chain has amino acids linked with each other in a specific sequence. This sequence of amino acids represents the primary structure of proteins.

(iii) Denaturation: It is the loss of biological activity of proteins because of some physical changes like changes in pH and temperature, due to which the unfolding of globules and the uncoiling of helix take place.
Examples: Coagulation of egg white on boiling and curdling of milk.