Question

Define the following as related to proteins:
(i) Peptide linkage
(ii) Primary structure
(iii) Denaturation

Answer 1

Hint : The amino acids are held together by a peptide bond. Proteins on hydrolysis give amino acids. Depending on the number of amino acids, they are classified into 3 types.

Complete step by step solution :
The molecules which yield amino acids on hydrolysis are called proteins. Proteins are the basis for major structural components of animal and human tissue. They are classified into three-simple, conjugated and derived proteins.
(i) The covalent bond that holds the amino acids together is called a peptide bond. Amino acids are the organic compound which has an amino group$\left( { - {\text{N}}{{\text{H}}_2}} \right)$, a carboxyl group$\left( { - {\text{COOH}}} \right)$ and a ${\text{R}}$ group which is a hydrocarbon. Carboxyl group of amino acid is connected with an amino group which releases a water molecule. It is produced by dehydration or condensation process. The resulting amide bond,${\text{CO}} - {\text{NH}}$, is called the peptide bond. Condensing or dehydrating two amino acids give peptide bonds.
(ii) Proteins are classified to four based on bonding between amino acids-primary, secondary, tertiary and quaternary. The sequence of amino acids in a polypeptide chain is called the primary structure of a protein.
(iii) Peptide bonds forming a spiral shape. This coiling is called secondary structure. Twisting or folding of polypeptide chains is termed as tertiary structure. The process in which there is a breakdown in the peptide bonds in secondary and tertiary structures is called denaturation. The primary structure of the protein will remain as such since this reaction is not so strong.
Additional information:
Simple proteins give one amino acid on hydrolysis. Conjugated proteins give an amino acid and a non-protein on hydrolysis. Derived proteins are derived from simple and conjugated proteins.

Note : Proteins act as a carrier of heredity materials from one generation to the next. Some proteins act as an oxygen carrier. Proteins obtained from soya beans are used for the production of plastics.