Structure of Proteins




Proteins are highly complex nitrogenous organic compound of very high molecular masses. All proteins are polymers of alpha amino acids.
Example: Glycine, Alanine, Valine etc.


Classify Proteins on the basis of Molecular structure

1) Fibrous proteins.
2) Globular proteins.


Definition and example of fibrous proteins

The proteins which consists of linear, thread like polypeptide chains arranged or twisted to form fibers are called fibrous proteins.
Example: Collagen in tendons, myosin in muscles etc.


Characteristics of fibrous proteins

1) Linear thread like structure.
2) Long chain is held together by hydrogen bond and some disulphide bonds.


Globular proteins

The proteins which consists of polypeptide chains folded in such a way so as to give a spherical shape to the protein molecule are called globular proteins.
All enzymes, several hormones such as insulin etc are example of globular proteins.


Characteristics of globular proteins

Globular proteins have some following characteristic:
1) Spheroidal shape
2) Interaction forces between different sites in the same polypeptides:
  a) Disulphides bridging 
  b) Hydrogen bonding
  c) Van der waals
3) These are soluble in water
4) They are very sensitive to change in temperature and pH


Denaturation of protein

Proteins when subject to external factors such as heat, alkalies, and several electrolytes, they undergo coagulation to form fibrous proteins which are insoluble in water. This leads to change in physical and biological properties of proteins. This type of proteins are called as denatured and process is called as denaturation.