Amino acids are the fundamental macromolecules of life, forming the backbone of proteins that constitute the majority of body mass. Twenty naturally occurring alpha‑amino acids are present in all living organisms, from bacteria to humans. Ten of these are synthesized by the body, while the other ten must be obtained from the diet and are therefore classified as essential amino acids. Deficiencies in essential amino acids can impair tissue synthesis and have been linked to disease states, including certain cancers.
Beyond their structural role, amino acids are a popular component of dietary supplements, especially among individuals seeking to enhance overall health or increase muscle mass through combined training and nutrition.
The first amino acid isolated was asparagine, discovered in asparagus juice in 1806. This landmark finding opened the door to the systematic study of amino acids.
All amino acids share a core structure: a central alpha‑carbon bonded to a carboxyl group, an amino group, a hydrogen atom, and a variable side chain (the R group). The carboxyl group (–COOH) is responsible for the acidic character of these molecules, while the amino group (–NH₂) contributes to their basic properties. The size of the side chain determines each amino acid’s chemical behavior.
The natural set of twenty amino acids is known as alpha‑amino acids because the amino group is attached to the alpha‑carbon adjacent to the carboxyl group. Their molecular weights range from 75 g/mol (glycine) to 204 g/mol (tryptophan), with an average smaller than the 180 g/mol of glucose. If all twenty were equally represented, each would account for 5 % of protein amino acid composition; actual frequencies vary from just over 1.2 % (tryptophan, cysteine) to nearly 10 % (leucine).
Amino acids are essential for protein synthesis, cellular structure, and numerous biochemical pathways. Understanding their structure and classification aids in grasping how proteins fold, function, and interact within the body.
