Principles of Biochemistry (2+1)

5.1.3 Classification of Proteins

5.1.3 Classification Proteins

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Proteins may be classified on the basis of their overall shape, number of polypeptide chains, solubility, biologic function, or three dimensional structures.

a.Classification based on shape 

 

a) Overall shape

Proteins are classified based on their overall shapes into globular proteins and Fibrous Proteins.

(i) Globular proteins

Globular proteins have compactly folded and coiled polypeptide chain with into axial ratios <than 10 (e.g. many enzymes,albumin & globulin). 

                                                                               

                                                                                          Myoglobin (Globular protein)

 

(ii) Fibrous proteins

Fibrous proteins are long stringy molecules with the polypeptide chains extended along one axis and have axial ratios greater than 10. Most fibrous proteins serve in a structural or protective role. Typical fibrous proteins are α- keratin of hair and wool, fibroin of silk, and collagen of tendons and connector tissues. eg. Keratin & collagen  

 

b) Number of polypeptide chains

            On the basis of the number of polypeptide chain present proteins are classified as monomeric or multimeric.

 

A protein that contains only one polypeptide is called a monomeric protein and that which contains more than one polypeptide chains is called a multimeric protein.