Definition of proteins :
- Proteins are compounds formed of Carbon, Hydrogen, Oxygen, Nitrogen, and may contain Sulphur.
- polymers which are formed of subunits called amino acids linked together by peptide bond.
Amino Acids :
Although more than 300 different amino acids have been described in nature, only 20 are commonly found as constituents of mammalian proteins. These are the only amino acids that are coded by DNA, the genetic material in the cell. Each amino acid has a carboxyl group, amino group and a side chain (“R group”) bonded to the α-carbon atom.
All amino acids are α-Amino acids.
At physiologic pH (approximately 7.4), the carboxyl group is
dissociated, forming the negatively charged carboxylate ion (–COO–), and the amino group is protonated (–NH3+).