Essential and Non – Essential Amino Acids

The requirement of essential amino acids differs from organism to organism. Some bacteria require only one amino acid in sufficient quantities in the growth medium to be able to synthesise the rest. In contrast mammals certainly cannot fulfil their protein requirements by only one amino acid. How can one determine which amino acid is essential and which is non-essential? The nutritional requirements are determined by deletion experiments i.e. by removing a single nutrient from the diet and then observing the growth and health of the animal. By this method it was found out that 10 amino acids are essential for the growth and well-being of rats.

Table:  Amino acids classified according to dietary needs of human and rats

Absence of anyone of these except arginine produces nutritional deficiency and even death. Rats are able to synthesise arginine but at such a slow rate that it does not meet the demands of normal growth. To what extent the animal requires a particular amino acid in diet depends on the synthetic ability of the body cells. Organisms with marked synthetic ability, for example, bacteria (mentioned earlier) require a few essential amino acids. Organisms like mammals, that require many essential amino acids have a marked synthetic disability.