Essential Amino Acids

Known as building blocks of protein, there are about 20 of them but only 9 are considered as essential amino acids. They cannot be produced by the body alone so human beings can only obtain them from foods or supplements.

Here are 7 of the 9 essential amino acids with a brief description of each:

amino acids


Coded for in the DNA, isoleucine has a chemical composition that is similar to that of leucine. However, the arrangement of its atoms is different which then has other properties. It is a hydrophobolic amino acid that thas two chiral centers. Meaning there are four stereoisomers and two diastereomers. It can be found in eggs, pork, mutton, chicken, pulses and beans.


Nutritionally one of the essential amino acids, leucine is isometric with isoleucine. Most commonly found in proteins, it is also significant in optimal growth especially in infancy and childhood, also in nitrogen balance in adults. It plays a major part in the maintenance of the muscles by equalizing synthesis and breakdown. Whole grains and milk products are its best sources.


Commonly found in proteins, lysine has a 4-aminobutyl side- chain classified together with arginine and histidine. Its human nutritional requirement is 1- 1.5 grams a day. Deficiency of which can lead to lack of niacin or vitamin B that causes a disease called pellagra. It can actually function as a nutritional supplement to help fight against herpes. It is obtained in most legumes, cereal grains and fish.


Lipotropic in nature, methionine is considered as one of the essential amino acids. Together with cyesteine, they are the only sulfur- containing proteinogenic amino acids. It has a part in carnitine and taurine synthesis by the processes called transsulfuration pathway, lecithin production and phosphatidylcholine synthesis. Astheroclerosis can be achieved if there is improper conversion of such. Meats, vegetables, nuts and legumes are its best supply.


Existing in two forms, phenylalanine are enantiomers or mirror- image molecules of one another. With a benzyl side- chain, its name was derived from its chemical structure composed of a phenyl group alternated for one of the hydrogens of alanine. Due to its phenyl group, it is considered as an aromatic compound. Its great sources are milk, avocados, pulses, legumes, nuts and seafoods.


One of the essential amino acids that contains two chiral centers, threonine has four possible stereoisomers and two diastereomers. With its name that can be used in a single enantiomer, its side chain can also undergo O- linked glycosylation. It can become phosphorylated through the action of a threonine kinase. Lentils, fish, meats and cheese are its best supply.


It may not be easily synthesized, tryptophan functions as building blocks in protein biosynthesis. A precursor for serotonin, melatonin and niacin, its functional group is indole. It has been implicated to bring about schizophrenia in persons that cannot be able to metabolize it correctly. It can be obtained in turkey, chicken, sesame , peanuts and chocolates.

amino acids
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