A protein can be defined as any substance which is made of amino acids in peptide linkage. The word "protein" comes from the Greek protos, "first," deservedly enough, as it is the basic constituent of all living cells. Protos may also be the root of the name of Proteus, a mythological figure who could change form; appropriately, food protein changes form to become human substance after being eaten.

Protein makes up three-fourths of the dry weight of most body cells. Proteins are also involved in the biochemical structure of hormones, enzymes, nutrient carriers, antibodies and many other substances and functions essential to life.

• 5-[[4-[2-(5-Ethyl-2-pyridinyl)ethoxy]benzyl}-2-imino-4-thiazolidinone
• HOBT (Monohydrate )
• DEPBT
• 4-Fluoro-L-phenylalanine
• 4-Fluoro-D-phenylalanine. HCl
• 4-Chloro-L-phenylalanine.HCl
• 4-Chloro-D-Phenylalanine.HCl

Simple proteins made up of only a few amino acids are called peptides. One should note that the word peptide comes from the Greek peptos, "cooked," a rather poetic way of referring to digestion. Peptides are often no more than digested proteins. Many peptides are absorbed directly into the bloodstream after eating. New roles for these very small proteins are being discovered almost daily, it seems. For example, many peptides work as neurotransmitters and as natural pain-relieving substances in the brain.

Scientists now know that protein as peptides can be absorbed immediately, without digestion, into the bloodstream. However, the majority of proteins are broken down into amino acids before absorption. It is these amino acids that are the primary building blocks of human life.

What Is an Amino Acid?

"Protein" is a well-recognized term, while the term "amino acid" can be confusing. Amino acids are made up of a weakly acid molecule group in conjunction with a strongly basic amino molecule group. The mild basicity or acidity of amino acids is too minimal to affect acid-base balance in the body, which is preserved by multitudes of protective buffer systems. Thus we hope the misnomer, "amino acid," will cease to confuse our readers.

Amino acids can be thought of as useful ammoniated vinegars. Glycine, for example, has a more correct chemical name: alpha aminoacetic acid. Since "amino" also means ammonia and acetic acid is vinegar, we can call this amino acid "ammoniated vinegar." This basic structure found in glycine is common to all amino acids. Smelling salts are usually ammonium carbonate, which can restore sensibility to people who have become faint. Vinegar, when added to salads and other foods, makes the taste of food more palatable. Similarly, some amino acids improve flavor or stimulate the mind. They also can control depression or produce sleep. Eight of the amino acids perform functions indispensable if the body is to stay alive; they are termed "essential" and must be consumed daily by everyone.

When acid or "vinegar" portions are removed from the amino acids, the basic amines become messengers in the nervous system. When the amine or ammonium portions are removed, the remaining "acid" can be used for fuel, detoxification, or in many processes throughout the body. The amino acids play innumerable roles in human health and disease.