Amino Acid
The molecular building blocks that link together to form peptides and proteins, each consisting of an amine group, a carboxyl group, and a unique side chain.
There are 20 standard amino acids used by the human body, and the specific sequence in which they are joined determines the shape and function of the resulting peptide or protein. In peptide research, the amino acid sequence of a compound directly dictates which receptors it binds and what biological effects it produces.
Many research peptides are synthetic analogs of naturally occurring amino acid sequences — researchers modify individual amino acids to improve stability, receptor affinity, or resistance to enzymatic degradation. Understanding amino acid composition helps explain why some peptides must be injected rather than taken orally, since digestive enzymes cleave amino acid bonds.