Write a general introduction and the importance of proteins.

(N/A) Proteins are the most abundant biomolecules in the living system. The chief sources of proteins are milk,cheese,pulses,peanuts,fish,meat,etc.
They occur in every part of the body and form the basis of the structure and functions of life. They are an important component for the growth and maintenance of the body.
The word protein is derived from the Greek word "proteios",which means primary or of prime importance. Proteins are polymers of $\alpha$-amino acids.
Amino acids contain amino $(-NH_{2})$ and carboxyl $(-COOH)$ functional groups. Depending upon the relative position of the amino group with respect to the carboxyl group,amino acids can be classified as $\alpha, \beta, \gamma, \delta$,and so on. Only $\alpha$-amino acids are obtained upon the hydrolysis of proteins. They may contain other functional groups as well.
All $\alpha$-amino acids have trivial names,which usually reflect the property of that compound or its source. For example,Glycine is so named since it has a sweet taste (in Greek,glykos means sweet),and Tyrosine was first obtained from cheese (in Greek,tyros means cheese). Amino acids are generally represented by three-letter symbols; sometimes,one-letter symbols are also used.
The general structure of an $\alpha$-amino acid is:
$R-CH(NH_{2})-COOH$
(where $R$ = side chain)