What are amino acids?

The most common amino acids in nature are known as α-amino acids. There are four different substituents attached to the central carbon atom (called the α-C atom) of such molecules:

"Amino group (NH₂, abbreviated" H- "for the three-letter code)."

The carboxylic acid group (COOH, abbreviated "-OH" in the three-letter code).

The side chain (R, which is highly variable and determines the nature of the amino acid and therefore the final peptide).

Hydrogen atom (H).

The attachment of the α-C atom to these four different groups gives it unique chemical properties, which play a key role in determining the behavior and properties of amino acids and peptides.
Biological activity of amino acids

Amino acids can exhibit biological activities, such as:

Tryptophan (Trp) and glutamate (Glu) play key roles in metabolic processes.

The R group, or side chain, determines the unique properties of the amino acid. These groups can:

Simply put: a hydrogen atom, such as glycine (Gly).

"They include other acids, such as aspartic acid (Asp) and glutamic acid (Glu)."

It carries a basic group: arginine (Arg), lysine (Lys), or histidine (His).

Contains polar groups such as serine (Ser) or threonine (Thr).

"They are non-polar hydrocarbons: alanine (Ala), phenylalanine (Phe), or valine (Val)."

Sulfur: as seen in cysteine (Cys) and methionine (Met).

The role of L-and D-amino acids

The four substituents of the α-C atom are arranged at the corners of the tetrahedron, with the α-C atom in the center (see FIG. 3). This arrangement allows the two forms of the amino acid molecule to exist in mirror images, similar to the left and right hands. These mirror forms are called "stereoisomers" or "enantiomers".

The biological importance of enantiomers

Although the chemical and physical properties of the enantiomers are nearly identical, their biological effects may differ significantly. Molecular shape is critical for its interaction with biological targets. One enantiomer may bind efficiently to the target, and the other may fail to bind, or in some cases have a negative effect. In solution, the enantiomer rotates the plane of polarized light in the opposite direction