In the medical field, the smallest building blocks of proteins are called amino acids. The amino acids are therefore absolutely necessary for the construction of proteins (synonym: proteins). Furthermore, amino acids are needed for the synthesis of enzymes and for the formation of certain messenger substances.
Chemically speaking, amino acids are a group of compounds characterized by the fact that they each have at least one amino group (-NH2) and one carboxyl group (COOH) in their structure. There are about 400 known amino acids in the world that occur naturally. The human organism needs about 20 amino acids for the various processes and the structure in the body.
These are therefore called proteinogenic amino acids. Mostly the proteinogenic amino acids are meant when we speak of amino acids in general. The 20 proteinogenic amino acids all have at least two carbon atoms (C).
The amino acids are divided into classes according to the carbon atom to which the amino group is attached. In the case of amino acids containing several amino groups, class membership is determined by the carbon atom whose amino group is spatially closest to the carboxyl group. Following this classification, three groups of amino acids are distinguished: Alpha-amino acids: The amino group is found here on the second carbon atom.
A simple example and important representative of alpha-amino acids is glycine, an amino acid with a very simple structure. All proteinogenic amino acids are assigned to the alpha-amino acids. This means that all human proteins are made of alpha-amino acids.
Beta-amino acids: In beta-amino acids, the amino group is located on the third carbon atom. Gamma-amino acids: The gamma-amino acids are defined by the fact that the amino group is located at the fourth carbon atom. From a chemical point of view, gamma-amino acids thus differ considerably from proteinogenic amino acids.
The gamma-amino acids are not used by the human body to build up proteins, so the gamma-amino acids are not proteinogenic amino acids. However, some amino acids of this class are found in humans. For example, gamma-aminobutyric acid (GABA) is a messenger substance in the brain.
- Alpha-amino acids: The amino group is found here on the second carbon atom. A simple example and important representative of alpha-amino acids is glycine, an amino acid with a very simple structure. All proteinogenic amino acids are assigned to the alpha-amino acids.
This means that all human proteins are made of alpha-amino acids. – Beta-amino acids: In beta-amino acids, the amino group is located on the third carbon atom. – Gamma-amino acids: The gamma-amino acids are defined by the fact that the amino group is attached to the fourth carbon atom.
From a chemical point of view, gamma-amino acids thus differ considerably from proteinogenic amino acids. The gamma-amino acids are not used by the human body to build up proteins, so the gamma-amino acids are not proteinogenic amino acids. However, some amino acids of this class are found in humans.
For example, gamma-aminobutyric acid (GABA) is a messenger substance in the brain. If we look at the molecular structure of the amino acids of all three classes, we find a very similar structure. However, due to certain differences in structure, they differ in their behaviour in acidic and basic environments.
The respective behaviour is determined by the structure of the side chains of the amino acids. The amino acids of one class all differ in the structure of their side chains. The amino acids which the human organism needs to build up proteins, i.e.
which are proteinogenic, can only be partially synthesized by the body itself (i.e. composed of raw materials). The amino acids that the body cannot synthesize itself are called essential amino acids. They have to be supplied by food.
The following amino acids are essential for adult humans: leucine, isoleucine, methyonine, threonine, valine, lysine, phenylalanine and tryptophan. Cysteine is a special case, as it can actually be synthesized by the body itself, but because it is an indispensable source of sulfur, it must be taken in anyway. Histidine and arginine are still essential for the immature human organism (i.e. infants).
Certain enzymes are needed to produce proteins from the amino acids. These enzymes place the amino acids in chains one after the other. The sequence of the different amino acids is different for each protein and determines the function and the application of the finished protein. The order in which the amino acids are put together is determined by the DNA.
