Amino acids are acid during which α-carbon is attached to the amino also because it is attached to R- group. They are the basic unit of proteins. Amino acids are basic units of protein. All amino acids have a minimum of one acidic acid (-COOH) group and one basic amino (-NH2) group. Amino acids are colourless, crystalline solid. They are soluble in water and insoluble in organic solvent. Only L- sort of amino acids are found in Proteins in physical body. If D-form is present, it's converted into l-form by enzymes in liver. More than 300 amino acids are found in nature but only 20 amino acids are standard and present in protein because they're coded by gene. Other non-standard amino acids are modified amino acids and called non-protein amino acids.  The last of the 20 common amino acids to be discovered was threatening in 1935 by William Cumming Rose, who also determined the essential amino acids and established the minimum daily requirements of all amino acids for optimal growth. In 1902, Emil Fischer and Franz Hofmeister independently proposed that proteins are formed from many amino acids, whereby bonds are formed between the amino of 1 terminological acid with the carboxylic of another, leading to a linear structure that Fischer termed "peptide". In the structure shown at the highest of the page, R represents a side chain specific to every terminological acid. The atom next to the carboxyl is named the α–carbon. Amino acids containing an amino bonded on to the alpha carbon are mentioned as alpha amino acids. These include amino acids like praline which contain secondary amines, which want to be often mentioned as "amino acids". Amino acids are designated as α- when the nitrogen atom is attached to the atom adjacent to the carboxyl group: during this case the compound contains the sub-structure N-C-CO2.