What are peptides? A plain-English guide
Peptides are short chains of amino acids that act as biological signals. Learn how they differ from proteins, how researchers use them, and the most common categories studied today.
A peptide is a short chain of amino acids joined by covalent peptide bonds. They sit between single amino acids and full-length proteins on the size spectrum and carry out a huge range of signaling roles in living systems — hormones, neuromodulators, immune messengers, and growth factors are all peptides.
Peptides vs. proteins
The line between a peptide and a protein is one of length and structure. Once a chain grows past roughly 50 amino acids and folds into a stable tertiary structure, it is conventionally called a protein. Below that, it is a peptide. Insulin (51 aa) is a famous edge case usually classified as a peptide hormone.
Categories researchers study
- Growth hormone secretagogues — e.g. CJC-1295, sermorelin, ipamorelin. Used in research on the GH/IGF-1 axis.
- Healing & repair peptides — e.g. BPC-157, TB-500. Studied for tissue and tendon recovery models.
- Metabolic peptides — GLP-1 analogs such as semaglutide and tirzepatide, studied in glucose and weight regulation.
- Cosmetic peptides — e.g. GHK-Cu, Melanotan II, used in skin and pigment research.
Why are peptides useful in research?
Peptides are highly selective. Because they often mimic the body's own signaling molecules, they can target a specific receptor with minimal off-target effects, making them powerful tools for in-vitro work.
Frequently asked questions
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