The word protein is derived from the Greek word ‘proteos’ meaning first. The name indicates that they are very essential for the growth and maintenance of the body. They occur in the protoplasm of the living cells. Proteins fulfil a wide range of functions such as mechanical movements, transporting cellular necessities such as oxygen, metal etc.
Based on solubility they are classified into two groups: Fibrous and Globular proteins.
Fibrous Proteins are insoluble in common solvents but are soluble in concentrated acids and alkalis. They are highly resistant to digestion by proteolytic enzyme.
Examples : Silk, Hair, Horn, Nails, Hoofs, Quills, Wool etc.
Read more: Fibrous vs Globular Proteins