Amino acids

What are amino acids? Chemical Structure

Amino acids (or amino acids) are the primary structural unit of proteins. We can therefore imagine the amino acids as bricks that, united by a glue called peptide bond, form a long sequence that gives rise to a protein.

Within the stomach and duodenum these bonds are broken and the individual amino acids reach up to the small intestine where they are absorbed as such and used by the body.

From the chemical point of view the amino acid is an organic compound containing a carboxylic group (COOH) and an amino group (NH ₂ ). In addition to these two groups, each amino acid is distinguished from the others by the presence of a residue (R) also known as the side chain of the amino acid.

Classification of amino acids

Only twenty of the various naturally occurring amino acids (currently over five hundred) are involved in protein synthesis. From the nutritional point of view, these amino acids can in turn be divided into two large groups: that of essential amino acids and that of non-essential amino acids.

Amino acids are defined as essential that the human body cannot synthesize in sufficient quantity to meet its own needs. For the adult there are eight and more precisely: phenylalanine, isoleucine, lysine, leucine, methionine, threonine, tryptophan and valine. During the period of growth to the eight mentioned, a ninth must be added, histidine, in consideration of the fact that in this period the requests for this amino acid are higher than the synthesis capacity.

Cysteine ​​and tyrosine are considered as semi-essential amino acids, since the body can synthesize them starting from methionine and phenylalanine.

These are conditionally essential amino acids (arginine, glycine, glutamine, proline and taurine) those amino acids that play a fundamental role in maintaining homeostasis and body functions in certain physiological situations. In some pathological conditions these amino acids may not be synthesized at sufficient speed to meet the real needs of the body.

Arginine is assuming considerable importance, as a precursor of nitric oxide, for the many functions that the latter performs in cellular activity, in the transduction of biological signals and in immune defense.

CONTENT IN ESSENTIAL AMINO ACIDS : those proteins containing all the essential AAs in quantity and in balanced relationships can be defined as complete or noble. In general, animal proteins are complete and plant proteins are incomplete. The noble wording associated with vegetable proteins is incorrect and was introduced to counter the saying that "legumes are the meat of the poor". In reality, taking a decent source of vegetable protein in the diet is very important and to further enhance this concept the term "noble" has been improperly introduced. In any case, these deficiencies can be overcome simply by using appropriate food associations such as PASTA and FAGIOLI. In this case we speak of mutual integration because the amino acids of which the pasta is lacking are supplied by the beans and vice versa.

AMINO ACID LIMITANTE: of a protein or a protein mixture it is the essential lacking or totally absent amino acid which limits the use of all the other amino acids even if present in excess with respect to the needs. As we have seen in the proteins of vegetable origin this amino acid is not generally sufficient to guarantee the needs and must be introduced through the combination with other foods.

CHEMICAL INDEX: it is given by the ratio between the quantity of a given amino acid in a gram of the protein under examination and the quantity of the same amino acid in a gram of the biological reference protein (of the egg). The higher this index, the greater the percentage of essential amino acids.

RAMIFIED AMINO ACIDS: o BCAAs are three essential amino acids (Valine, Isoleucine and Leucine) which, under particular conditions, such as intense physical effort, are used as an auxiliary energy substrate of fats and carbohydrates.

Functions of amino acids

The primary function of amino acids is to intervene in protein synthesis, necessary to cope with the body's cellular renewal processes. In addition to this function, called "plastic", amino acids also have a modest but not negligible importance in energy production (branched amino acids)

Some amino acids are also precursors of compounds that perform important biological functions.

From the tryptophan niacin (vitamin PP), serotonin (neurotransmitter) and melatonin (regulator of the circadian rhythms sleep / wake cycle) are obtained.

Glutathione is obtained from sulfur amino acids (methionine and cysteine), an important antioxidant useful for fighting free radicals and keratin, an essential protein for the health of hair, hair and nails.

In addition to those involved in protein synthesis, many other amino acids perform very important functions. Among these the most known in the sports field are creatine (useful for increasing capacity and anaerobic alattacid and lactic acid power) and carnitine which facilitates the transport of lipids within the mitochondria).

CONTINUE: Functions of amino acids »