Proteins are the most abundant bio molecules of the living system.All proteins are polymers of
Structure of proteins: Two amino acids are linked together by peptide linkage.It is formed between -COOH group and the -NH2 group.
A polypeptide( many amino acids linked) with more than hundred amino acids joined and having molecular mass higher than 10,000 u is called a protein.
Classification of structure of proteins:
1)primary structure: Each amino acid in a protein is linked with another in a particular sequence and this is primary structure of that protein.Any change in this structure creates a different protein.
2)secondary structure: is the shape in which polypeptide chains exist..
3)Tertiary structure:Represents the irregular folding of the secondary structure.
Gives rise to two shapes of proteins:
Fibrous- polypeptide chains run in parallel and are held together by hydrogen,di-sulphide bonds.generally insoluble in water. examples: keratin, myosin.
Globular- chains of polypeptide coil around to give a spherical shape usually soluble in water.examples:insulin,albumin.
4)Quaternary structure: Refers to the spatial arrangement of two or more polypeptide chains grouped together(also called sub units).