Classification of Amino Acids
Amino acids are classified into different ways based on polarity, structure, nutritional requirement, metabolic fate, etc. Generally used classification is based on polarity. Amino acid polarity chart shows the polarity of amino acids.
Based on polarity, amino acids are classified into four groups as follows,
- Non-polar amino acids
- Polar amino acids with no charge
- Polar amino acids with positive charge
- Polar amino acids with negative charge
Non Polar Amino Acids have equal number of amino and carboxyl groups and are neutral. These amino acids are hydrophobic and have no charge on the 'R' group. The amino acids in this group are alanine, valine, leucine, isoleucine, phenyl alanine, glycine, tryptophan, methionine and proline.
These are some of the properties of non polar amino acids.
These amino acids do not have any charge on the 'R' group. These amino acids participate in hydrogen bonding of protein structure. The amino acids in this group are - serine, threonine, tyrosine, cysteine, glutamine and aspargine.
Polar amino acids with positive charge have more amino groups as compared to carboxyl groups making it basic. The amino acids, which have positive charge on the 'R' group are placed in this category. They are lysine, arginine and histidine.
Polar amino acids with negative charge have more carboxyl groups than amino groups making them acidic. The amino acids, which have negative charge on the 'R' group are placed in this category. They are called as dicarboxylic mono-amino acids. They are aspartic acid and glutamic acid.
