Peptides vs. Proteins vs. Amino Acids

Amino acids are the individual building blocks. When a small number of them link together, the result is a peptide. When many link together and fold into complex shapes, the result is a protein.

The line between a long peptide and a small protein is not rigid, but size and structural complexity are the general distinguishing factors.

Understanding this hierarchy helps make sense of the broader science literature, where these terms appear frequently.