Amino Acids

Amino acids are critical to life.  They have many functions in metabolism, carrying genetic codes, and as the building blocks of proteins. 

Of the 22 standard amino acids, 9 are called essential amino acids.  it is because the human body CANNOT synthesize them from other compounds at the level needed for normal growth, so they must be obtained from food.  The 9 essential amino acids are: Histidine, Isoleucine, Leucine, Lycine, Methionin, Phenyalanine, Threonine, Tryptophan, and Valine.

Arginine, Cysteine, Taurine, and Tyrosine are semi-essential amino acids in children, because the metabolic pathway that synthesize them are not fully developed.  Thus children must obtain them from food.

Taurine is not exactly an amino acid, although it is an acid containing an amino group, yet lacks of a carboxyl group. 

Glutamine, Selonocysteine, and Serine too are semi-essential amino acids.  They become conditionally essentially in certain situations, eg. intensive athletic training, certain gastrointestinal disorders, liver disorders, metabolic diseases, physical stress etc  

Alanine, Asparagine, Aspartic Acid, Glutamic Acid, Glycine, Ornithine, and Proline are non-essential amino acids, meaning they can be manufactured by the human body, and do not need to be obtained directly through the diet.

Amino acids bond together into chains polypeptides. One or more polypeptides folded into globular or fibrous form biochemical compound called proteins.

Vegans, peoples on low protein diets, peoples with eating disorders, or diseased are often be at risk of deficient of essential and semi-essential amino acids.  Although the non-essential amino acids can be manufacture by human body, deficiency may still occur if intake of protein foods are insufficient.

Deficiency of amino acids may cause enzyme disorders, hormone disorders, metabolic disorders, which leads to headaches, dizziness, fatigues, growth disorder, reproduction problems, hair and nail disorders, organ disorders, failure of immune functions, even depression and mental retardation.

Foods rich in amino acids are : eggs, meats, poultries, dairy products, seafood, legumes, seeds, and some vegetables and fruits.