Histidine and arginine are required for growing children. They are semi or partially essential. Arginine is involved in urea cycle.

The acronym of the following amino acids is MILLPHTTV. M–Methionine I–Isoleucine L–Leucine L–Lysine P–Phenylalanine H–Histidine T–Tryptophan T–Threonine V–Valine

Essential or indispensable Carbon skeletons are not synthesised by human beings, so amino acids are taken in food for normal growth.

Example: Lys, Ile, Phe, and Tyr are partially ketogenic and partially glucogenic

Enter into glucogenic pathway. Example: Glu, Ala, Val, Ser, Thr, Cys, Met, Asn, Gln, Asp, Glu, Arg, His, and Pro.

Purely ketogenic Example: Leu, which enters into the metabolic pathway of fat.

The side chain contains extra amino group, which has important basic properties to them. Example: Lys, Arg, and His

R—contains extra COO− group with dissociable behaviour. Example: Asp and Glu

R—amino acid is soluble in water because it contains functional group that forms H2 bond with H2O. Example: Gly, Ser, Thr, Cys, Tyr, Gln, and Asn

R—group in this category is hydrocarbon in nature and thus hydrophobic (water repellent) and lipophilic. Example: Ala, Val, Leu, Ile, Pro, Phe, Trp, and Met