Amino acids are the building blocks of life. They are the tiny components from which proteins such as enzymes and neurotransmitters are made. They have a place at the very centre of human metabolism and are an integral part of almost any physiological process.
Altogether there are more than 200 amino acids, of which 22 form tissue such as muscles, skin, blood vessels, tendons, hair, etc. These are called proteinogenic amino acids.
In contrast to the other two energy-carriers, carbohydrates and fats, amino acids and proteins contain nitrogen atoms (chemical symbol N). This is why they are so important: they are the body’s only source of the nitrogen, which is essential to life.
These are the main functions of amino acids and proteins:
They are the building blocks of muscles, tendons, ligaments, skin, hair and connective tissue. Keratin, which forms hair structure, is made of amino acids.
Amino acids are the building blocks of DNA, which holds all our genetic information.
Amino acids repair injured tissue.
Amino acids are intimately involved in the immune system, being the building blocks of the immune cells.
Amino acids are the basic material for enzymes, participating in practically all metabolic changes.
Amino acids are the foundation of hormones, chemical messengers that carry reactions to specific parts of the body.
Amino acids are transportation molecules.
Amino acids can also supply energy.
ESSENTIAL AND NON-ESSENTIAL AMINO ACIDS
All together there are over 200 distinct amino acids. However, for the sake of brevity only the most important ones, the protein-making amino acids, are listed here. According to their importance for the human body amino acids are divided into 'essential' and 'non-essential' categories. Essential amino acids cannot be produced by the human body, whereas non-essential amino acids can.
Amino acids can exist in two forms, the D-form (dextrorotary) and the L-form (levorotary, the mirror image of the D-form). The D-form is not used by the body and can often be harmful or toxic. Only the L-form is used by the body.
It is therefore important to be careful when discussing amino acids on a high level: one might neglect to specify an L-amino acid and merely refer to arginine, for example. But really L-arginine, the levorotary form which can be metabolised by the human body, is almost always meant.
Essential amino acids
The category of essential amino acids comprises:
Semi-essential amino acids
L-arginine, L-cysteine, L-taurine and L-tyrosine are often referred to as 'semi-essential' amino acids in children because the body is able to produce them in certain quantities. In healthy individuals the body is mostly able to synthesise sufficient quantities itself from other amino acids.
During times of illness or intense stress, however, the body cannot produce enough of these amino acids and relies on additional supplementation through the diet. At ages above 40, the required amount of L-arginine increases, which is also a factor making L-arginine an essential and important part of the daily diet.
Non-essential amino acids
The category of non-essential amino acids comprises:
Even though these amino acids are non-essential they have a significant influence as part of the diet over the metabolic processes, health and well-being. In addition, the non-essential amino acids may quickly become indispensable when amino acids are absent in the diet, which the body needs as building blocks to produce its others. It should therefore be noted that some researchers regard the classification as being useful in practice.
L-arginine is one of the most intensively studied amino acids. Again, whenever the term 'arginine' is used it should be taken to mean 'L-arginine', the levorotary form which the body can metabolise. When L-arginine is under study the quality of both raw materials and manufacturing processes employed are of essential importance for the quality of the final product.
L-arginine is so important for the reason that of all the amino acids it contains the highest percentage of nitrogen (N). The body specifically requires nitrogen for the synthesis of the vasodilator nitrous oxide (NO). Among other necessities for the body L-arginine promotes the synthesis of (NO) receptor-activators. NO regulates muscle tension in the blood vessel walls (endothelium) and thus the dilation of the blood vessels, which determines the rate of blood flow. The body has no substitute for L-arginine as a trigger for the vasodilation control process.
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