Amino acids are biologically important organic compounds composed of amine (-NH2) and carboxylic acid (-COOH) functional groups, along with a side-chain specific to each amino acid.
The key elements of an amino acid are carbon, hydrogen, oxygen, and nitrogen, though other elements are found in the side-chains of certain amino acids.
[Here, O= oxygen, C= carbon, N= nitrogen H= Hydrogen, R= the side group attached to the amino acid.]
The figure below tries to show the peptide bond formation by two amino acid molecules:
There are about 500 amino acids. Of these 22 are standard amino acids. Nine of the 22 standard amino acids are called “essential” for humans because they cannot be created from other compounds by the human body and, so, must be taken in as food.
On the basis of their structure and the general chemical characteristics of their R groups (side chains), amino acids can be assorted into six main groups. They are:
Name of the amino acids
|Aliphatic||Glycine, Alanine, Valine, Leucine, Isoleucine|
|Hydroxyl or Sulfur/Selenium-containing||Serine, Cysteine, Selenocysteine, Threonine, Methionine|
|Aromatic||Phenylalanine, Tyrosine, Tryptophan|
|Basic||Histidine, Lysine, Arginine|
|Acidic and their Amide||Aspartate, Glutamate, Asparagine, Glutamine|