Principles of Biochemistry

4.2.4 Essential and Nonessential Amino Acids

For nutritional purposes, amino acids may be divided into two groups, essential amino acids (EAA), and the non-essential amino acids (NEAA). The essential amino acids are that, which cannot be synthesized within the animal body or synthesised in sufficient amounts to meet the physiological needs of the growing animal, therefore must be supplied in the diet.There are 10 essential amino acids (indispensible). The remaining 10 are non-essential amino acids (dispensible) as they can be synthesized in animals from other compounds. A complete protein is a protein that contains all the essential amino acids in approximately the same relative amounts in which the human body needs them.

Most animal proteins, including case in from milk and proteins found in meat, fish, eggs, are complete proteins. Proteins from plants(vegetables, grains and legumes) have quite diverse amino acid patterns and some tend to be limited in one or more essential amino acids. In cereals, lysine is the limiting amino acid while in pulses it is methionine.

Essential amino acids(EAA)	Non-essential amino acids (NEAA)
Methionine	Glycine
Tryptophan	Cysteine
Threonine	Alanine
Valine	Serine
Isoleucine	Proline
Ieucine	Tyrosine
Phenylalanine	Aspartic acid
Lysine	Asparagine
Arginine	Glutamic acid
Histidine	Glutamine