ABSTRACT
Proteins are polymers made up of linear sequences of amino acids. There are 20 basic amino acids (see Table 1) which are considered the essential building blocks for the great multitude of possible protein combinations. All amino acids contain nitrogen atoms, therefore the proteins represent a class of nitrogenous compounds. Linkage of the amino acids is by means of a peptide bond (Fig. 1) and so the polymer is a polypeptide chain. Proteins constitute as much as two-thirds of the dry weight of cells and their molecular weights vary from fairly small structures, as for instance the insulin molecule, to very large configurations having molecular weights in excess of one million. Amino Acids
Alanine (Ala)
Glycine (Gly)
Proline (Pro)
Arginine (Arg)
Histidine (His)
Serine (Ser)
Asparagine (Asp-NH2,Asn)
Isoleucine (lie)
Threonine (Thr)
Aspartic acid (Asp)
Leucine (Leu)
Tryptophan (Trp)
Cysteine (Cys)
Lysine (Lys)
Tyrosine (Tyr)
Glutamic acid (Glu)
Methionine (Met)
Valine (Val)
Glutamine (Glu-NH2,Gin)
Phenylalanine (Phe)
Source: From Refs. 2a and 2b. Linkage of amino acids by means of a peptide bond. https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9780203753699/85a9a6bc-cc25-40df-b58d-669bc048989c/content/fig4_1_OB.tif"/>