Amino acid

Definition

An organic compound containing both an amino group (–NH₂) and a carboxylic acid group (–COOH), serving as the monomeric building block of proteins. In arthropods, the 20 standard proteinogenic amino acids are incorporated into structural proteins (cuticle, silk), enzymes, venom peptides, and pheromone precursors; essential amino acids must be obtained through diet or symbiotic microbes.

Etymology

From amino (containing nitrogen, from ammonia) + acid (carboxylic acid functional group)

Example

The silk proteins of spiders (Araneae) and silkworms (Bombyx mori) are rich in the amino acids glycine and alanine, whose small side chains allow tight packing into the β-sheet crystallites that give silk its tensile strength.

Synonyms

• α-amino acid

Related Terms

• protein
• peptide
• essential amino acid
• Cuticle
• venom
• Pheromone
• nitrogen metabolism
• silkworm
• spider silk

Usage Notes

Distinguish between proteinogenic amino acids (incorporated into proteins via ribosomal translation) and non-protein amino acids such as γ-aminobutyric acid (GABA, a neurotransmitter) or D-amino acids found in bacterial peptidoglycan and some arthropod antibiotics. In nutritional ecology, insects vary widely in essential amino acid requirements; phytophagous species often rely on gut symbionts to supplement limiting amino acids like methionine or tryptophan.