Spheres of Science

The amino (pronounced ah meen'-o) acids are much more closely associated with the fundamental life processes than are the now well known A-B-C-D-E variety, for they not only take part in the vital chemical processes, as do the lettered kind, but to a vastly greater extent they are a part of the structural fabrics of living tissue.

The stuff of life is protoplasm. Protoplasm is made up of a variety of protein substances and all proteins are composed of amino acids which are probably the most interesting and versatile molecules with which chemists work. They have a many-sided personality and could be considered the geniuses among molecules.

A relatively simple structure characterizes the amino acids. They consist of a chain of carbon atoms, of variable length, at one end of which is a "head" which, with slight differences, is common to all of them. They all differ in the structure of the chain, or "body" and these differences in structure give to each one its unique set of chemical properties. Some of them are double-enders and have tail structures that resemble, in whole or in part, the head end.

The head of an amino acid molecule, like the Janus of mythology, is two-faced. The two faces exhibit completely opposite chemical personalities. One is basic and the other acidic, a situation which makes the molecule very versatile. One is water-loving and the other water-hating. One can cooperate with water-soluble substances and the other with fat or oil-soluble materials. The acidic part of the head is made up of four atoms, known as carboxyl group, one carbon, two oxygen and one hydrogen. The basic part of the head is made up of an amino group, composed of a nitrogen and two hydrogen atoms (just one step removed from ammonia).

The most common unit forming the chain, or body, is a carbon atom with two hydrogen atoms attached, but a number of the amino acids have nitrogen atoms in the chain, or attached to it, a few have sulphur atoms in the chain, and a few include one or more rings of atoms.

The first step toward creating a structure that manifests the mysterious vital properties of life is taken when amino acids link themselves together in a chain, the acidic head of one uniting with the basic head of the next. These chains unite with other chains to form the very complex structure of a protein molecule containing tens of thousands or even hundreds of thousands of the amino acids.

Protein molecules are the building blocks of cells, and cells are the building blocks of which muscles, organs and other parts of all living things are constructed.

The structure of protein molecules is unknown but it is known that it is highly organized, perhaps as the simplest self-sustaining living organism although it probably could not be maintained as a living entity outside a more complex living organism.

Recent researches indicate that the protein molecule possesses something which may be characterized as a head, and it also has a body in which digestive processes of nutrition are carried on.

The head can be visualized as the prosthetic group which consists of a vitamin and an enzyme. This is the part of the protein molecule that takes the simple substances, amino acids, sugars, minerals, etc., from the blood stream and builds them into the structure of the molecule. It may be the point at which the long

chains are knitted for the molecule's body. The protein molecule is a self-consuming organism. The atoms in the chain that dangles from the head are its nutrient material. When these are consumed the head disintegrates and a new chain of amino acids must be manufactured by the prosthetic group.

To build these structures essential to life and growth and maintenance of living structures, it is essential that the body receive in its food the amino acids which the prosthetic groups are unable to manufacture and which are, therefore, dietary essentials.

There are ten essential amino acids and these are the ones which are likely to enjoy a period of glamour existence. A vitamin is a substance essential to life which the body is unable to manufacture, so the amino acids are vitamins in the same sense as thiamin, ascorbic acid, niacin, etc.

All Found in Common Foods

The vitamin amino acids and the relative amounts of each required by the body are: lysine, 10; leucine, 9; phenylalanine, 7; valine, 7; threonine, 6; methionine, 6; isoleucine, 5; histidine, 4; tryptophane, 2, and arginine, 2.

Lack of any one of these vitaminos (to coin a new word) leads to a deficiency disease, growth failure and physical deterioration. All of them are available in common food sources. Lack of the lettered vitamins may make it impossible for the body to utilize the vitaminos and, conversely, lack of the vitaminos may make it impossible for the vitamins to perform their essential functions in the nutrition of the body.

Amino acids which the body uses but is able to manufacture are alanine, aspartic acid, citrulline, cystine, glutamic acid, glycine, hydroxyglutamic acid, hydroxyproline, norleucine, proline, serine and tyrosine.

The amino acids are the substances from which the body makes the hormones and other life-essential fluids. The vitaminos, if received in the right proportion, comprise about 6 per cent of the minimum adequate diet.-John J. O'Neill, in The New York Herald Tribune.