Define the following as related to proteins.
(i) peptide linkage
(ii) Denaturation.

Answer

(i) Peptide bond Proteins are condensation polymers of alpha -amino acids in which the same or different alpha-amino acids are connected by peptide bonds Chemically a peptide bond is an amide linkage formed between `-COOH` group of one `alpha` amino and `-HN_(2)` group of the other `alpha` -amino acid by loss of a molecules of water For example
`(##RES_ORG_CHM_V02_XII_C04_E01_223_A01##)`
(ii) Each protein in the biological system has a unique three-dimensional structure and has specific biological activity This is called native form of a ptotein When a protein in its native form is subjected to physical changes such as change in temperature `pH` etc hydrogen bonds are broken Due to cleavage of hydrogen bonds unfolding of protein molecule occurs and ther protein loses its biological activity This loss of biological activity is called denaturation During denaturation `2^(@)` and `3^(@)` biological activity This loss of biological activity is called denaturation During denaturation `2^(@)` and `3^(@)` structures of proteins are destroyed `1^(@)` structure remains intact As a result of denaturation globular proteins (soluble in `H_(2)O)` are converted into fibrous proteins (insoluble in `H_(2)O)` In other words denaturation leads to coagulation That is why coagulated proteins are also called denaturated proteins.