Proteins are described as essential and nonessential proteins or amino acids. The human body requires approximately 22 amino acids in specific patterns for the synthesis of its proteins.
In the human body, the liver produces about 80 percent of the amino acids needed. The remaining 20 percent must be obtained from the diet.
These are called the essential amino acids, because human body cannot make them and must get them in the diet.
They are methionine, threonine, tryptophan, leucine, isoleucine, lysine, valine, phenylalanine and histidine.
The processes of assembling amino acids to make proteins and of breaking down proteins into individual amino acids for the body’s use are continuous ones.
Should the body become depleted of its reserves of any of the essential amino acids, it would not be able to produce the proteins that require those amino acids.
While the presence of essential amino acids is critical to protein synthesis, there is some evidence that lack of the nonessential amino acids can result in lower plasma level of these amino acids, which may ultimately compromise proteins synthesis in situations where there is rapid growth.
Sometimes, certain nonessential amino acids can become essential.
This is true of nonessential amino acids that are synthesized from other amino acids or when synthesis is limited due to special physiological conditions. Tyrosine and cysteine are both considered conditionally essential amino acids.
Essential amino acids
