Essential amino acids
Of the 20 amino acids found in proteins, 9 are considered to be essential. This means they cannot be synthesised by vertebrates and are acquired from other organisms, such as plants, as part of a vertebrate's diet.
The 9 essential amino acids are histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan and valine.
| Amino Acid | Single letter code | Three letter code | Charge (+/-/neutral) | Polar/ nonpolar |
|---|---|---|---|---|
| Histidine | H | His | +ve | polar |
| Isoleucine | I | Ile | neutral | nonpolar |
| Leucine | L | Leu | neutral | nonpolar |
| Lysine | K | Lys | +ve | polar |
| Methionine | M | Met | neutral | nonpolar |
| Phenylalanine | F | Phe | neutral | nonpolar |
| Threonine | T | Thr | neutral | polar |
| Tryptophan | W | Trp | neutral | nonpolar |
| Valine | V | Val | neutral | nonpolar |