What is an essential amino acid?

Answer 1

An essential amino acid is a building block of protein molecules that our bodies cannot produce and need to get from a food source. They are essential because we can not synthesize them from other amino acids or smaller building blocks. Ultimately they are needed to make proteins which build tissues in our bodies.

Answer

Protein molecules are long chains of amino acids. There are 20 naturally occurring amino acids used in protein synthesis alanine, asparagine, aspartic acid, glutamic acid, cysteine, glutamine, glycine, proline, serine, tyrosine, arginine and histidine are non essential in that they can be synthesized from precursors in the diet. The amino acids isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan and valine can not be synthesised by the body and therefore must be essential components of the diet. However some of the nonessential amino acids listed above are essential for normal growth in children since they do not have full biosynthetic capability as they develop.

Answer

Amino acids which can't be synthesized by the body and must be taken in diet are known as essential amino acids.
Essential amino acids are required by animals yet they cannot be synthesized, they are usually supplied in the diet.