Amino Acids

James Richard Fromm

An AMINO ACID is by definition an organic compound containing an amine group and a carboxylic acid group in the same molecule. While there are many forms of amino acids, all of the important amino acids found in living organisms are alpha-amino acids. Alpha amino acids have the -COOH and -NH2 groups both attached to the same carbon atom, called the alpha carbon atom. The simplest amino acid, which is the molecule glycine, H2NCH2COOH, contains no asymmetric carbon atoms (tetrahedral carbon atoms with four different groups attached). All of the other amino acids do contain such a carbon atom and are therefore optically active. The general structure of the alpha-amino acids is R-CHNH2(alpha)-COOH, and optical activity for the alpha-amino acids more complex than glycine is found at the alpha carbon. The amino acids which have been found to be incorporated into the proteins of living organisms are listed in the Table below.

Table: Amino Acids Found to Be Incorporated Into Proteins
Name (Abb.) R Group Class Synthesis
Glycine (Gly) H- Hydrocarbon Yes
Alanine (Ala) CH3- Hydrocarbon Yes
Valine (Val) (CH3)2CH- Hydrocarbon No
Leucine (Leu) (CH3)2CH2CH2- Hydrocarbon No
Isoleucine (Ile) CH3CH2CH(CH3)- Hydrocarbon No
Aspartic Acid (Asp) HOOCCH2- Acidic Yes
Glutamic Acid (Glu) HOOCCH2CH2- Acidic Yes
Lysine (Lys) H2N(CH2)4- Basic No
Arginine (Arg) HN=C(NH2)NH(CH2)3- Basic No
Histidine* (His) Ring Structure Basic No
Phenylalanine (Phe) C6H5CH2- Aromatic No
Tyrosine* (Tyr) HOC6H5CH2- Aromatic Yes
Tryptophan* (Trp) Ring Structure Aromatic No
Serine (Ser) HOCH2- Alcohol Yes
Threonine (Thr) HOCH(CH3)- Alcohol No
Methionine (Met) H3CSCH2CH2- Sulfur No
Cysteine (Cys) HSCH2- Sulfur No
Asparagine (Asp) H2NCOCH2- Amide Yes
Glutamine (Gln) H2NCOCH2CH2- Amide Yes
Proline* (Pro) Heterocyclic Ring Unique Yes
Note: the hydroxyl group is para on the ring in tyrosine.      

AMINO ACIDS have both an acidic group, in the carboxylic acid, and a basic group, in the amine. Under physiological aqueous conditions a proton transfer from the acid to the base occurs, forming a dipolar ion or zwitterion, because the carboxylic acid is a much stronger acid than is the ammonium ion. The actual structure of glycine in solution, for example, is +H3NCH2COO- at pH 7 rather than H2NCH2COOH. At very low pH the acid group can be protonated and at very high pH the ammonium group can be deprotonated, but the forms of amino acids relevant to living organisms are the zwitterions.

Each asymmetric carbon gives rise to two optical isomers which are traditionally distinguished by the letters D or L. Only those amino acids which are the L forms (left-handed) at the alpha carbon are found in terrestrial life.

glycine (Gly)

alanine (Ala)

valine (Val)

leucine (Leu)

isoleucine (Ile)

aspartic acid (Asp)

glutamic acid (Glu)

lysine (Lys)

arginine (Arg)

histidine* (His)

phenylalanine (Phe)

tyrosine* (Tyr)

tryptophan* (Trp)

serine (Ser)

threonine (Thr)

methionine (Met)

cysteine (Cys)

asparagine (Asp)

glutamine (Gln)

proline* (Pro)


thyroxine (Thy)

taurine (Tau)


AMINO ACIDS are the "building Blocks" of the body. Besides building cells and repairing tissue, they form antibodies to combat invading bacteria & viruses; they are part of the enzyme & hormonal system; they build nucleoproteins (RNA & DNA); they carry oxygen throughout the body and participate in muscle activity. When protein is broken down by digestion the result is 22 known amino acids. Eight are essential (cannot be manufactured by the body) the rest are non-essential ( can be manufactured by the body with proper nutrition).

TRYPTOPHAN (Essential Amino Acid) A natural relaxant, helps alleviate insomnia by inducing normal sleep; reduces anxiety & depression; helps in the treatment of migraine headaches; helps the immune system; helps reduce the risk of artery & heart spasms; works with Lysine in reducing cholesterol levels.

LYSINE (Essential Amino Acid) Insures the adequate absorption of calcium; helps form collagen ( which makes up bone cartilage & connective tissues); aids in the production of antibodies, hormones & enzymes. Recent studies have shown that Lysine may be effective against herpes by improving the balance of nutrients that reduce viral growth. A deficiency may result in tiredness, inability to concentrate, irritability, bloodshot eyes, retarded growth, hair loss ,anemia & reproductive problems.

METHIONINE (Essential Amino Acid) Is a principle supplier of sulfur which prevents disorders of the hair, skin and nails; helps lower cholesterol levels by increasing the liver's production of lecithin; reduces liver fat and protects the kidneys; a natural chelating agent for heavy metals; regulates the formation of ammonia and creates ammonia-free urine which reduces bladder irritation; influences hair follicles and promotes hair growth.

PHENYLALAINE (Essential Amino Acid) Used by the brain to produce Norepinephrine, a chemical that transmits signals between nerve cells and the brain; keeps you awake & alert; reduces hunger pains; functions as an antidepressant and helps improve memory.

THREONINE (Essential Amino Acid) Is an important constituent of collagen, Elastin, and enamel protein; helps prevents fat build-up in the liver; helps the digestive and intestinal tracts function more smoothly; assists metabolism and assimilation.

VALINE (Essential Amino Acid) Promotes mental vigor, muscle coordination and calm emotions.

LEUCINE & ISOLEUCINE (Essential Amino Acid) They provide ingredients for the manufacturing of other essential biochemical components in the body, some of which are utilized for the production of energy, stimulants to the upper brain and helping you to be more alert.

ARGININE (Non-Essential Amino Acid) Studies have shown that it has improved immune responses to bacteria, viruses & tumor cells; promotes wound healing and regeneration of the liver; causes the release of growth hormones; considered crucial for optimal muscle growth and tissue repair.

TYROSINE (Non-Essential Amino Acid) Transmits nerve impulses to the brain; helps overcome depression; Improves memory; increases mental alertness; promotes the healthy functioning of the thyroid, adrenal and pituitary glands.

GLYCINE (Non-Essential Amino Acid) Helps trigger the release of oxygen to the energy requiring cell-making process; Important in the manufacturing of hormones responsible for a strong immune system.

SERINE (Non-Essential Amino Acid) A storage source of glucose by the liver and muscles; helps strengthen the immune system by providing antibodies; synthesizes fatty acid sheath around nerve fibers.

GLUTAMIC ACID (Non-Essential Amino Acid) Considered to be nature's "Brain food" by improving mental capacities; helps speed the healing of ulcers; gives a "lift" from fatigue; helps control alcoholism, schizophrenia and the craving for sugar.

ASPARTIC ACID (Non-Essential Amino Acid) Aids in the expulsion of harmful ammonia from the body. When ammonia enters the circulatory system it acts as a highly toxic substance which can be harmful to the central nervous system. Recent studies have shown that Aspartic Acid may increase resistance to fatigue and increase endurance.

TAURINE (Non-Essential Amino Acid) Helps stabilize the excitability of membranes which is very important in the control of epileptic seizures. Taurine and sulfur are considered to be factors necessary for the control of many biochemical changes that take place in the aging process; aids in the clearing of free radical wastes.

CYSTINE (Non-Essential Amino Acid) Functions as an antioxidant and is a powerful aid to the body in protecting against radiation and pollution. It can help slow down the aging process, deactivate free radicals, neutralize toxins; aids in protein synthesis and presents cellular change. It is necessary for the formation of the skin, which aids in the recovery from burns and surgical operations. Hair and skin are made up 10-14% Cystine.

HISTIDINE (Non-Essential Amino Acid) Is found abundantly in hemoglobin; has been used in the treatment of rheumatoid arthritis, allergic diseases, ulcers & anemia. A deficiency can cause poor hearing.

PROLINE (Non-Essential Amino Acid) Is extremely important for the proper functioning of joints and tendons; also helps maintain and strengthen heart muscles.

ALANINE (Non-Essential Amino Acid) Is an important source of energy for muscle tissue, the brain and central nervous system; strengthens the immune system by producing antibodies; helps in the metabolism of sugars and organic acids.

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Copyright 1997 James R. Fromm