Amino acid derivatives are compounds formed from amino acids, which are the building blocks of proteins. These derivatives can include modifications such as methylation or phosphorylation, altering the original amino acid's structure and function. They play crucial roles in various biological processes, including metabolism and signaling. Some common amino acid derivatives include neurotransmitters like serotonin and dopamine, which are derived from specific amino acids. Additionally, derivatives can serve as precursors for important biomolecules, such as hormones and enzymes, contributing to the overall functioning of living organisms.