Scientists Say: Peptide

These tiny chemical chains are the building blocks of proteins and more


This is the chemical structure of pepsin, a large molecule that breaks down proteins into smaller peptides. The pepsin molecule is itself made of peptides, here shown in different colors.


Peptide (noun, “PEP-tie-d”)

This is a short chain of amino acids — the simple molecules that make up proteins. Amino acids link together in strings. A short string from two to about 100 amino acids earns the name “peptide.”

Peptides can hold many roles in a cell. They can join forces to make up a larger protein. When those proteins are broken down, the trash products are peptides. Peptides can also do work alone. Some small peptides serve as messengers between cells in the brain and body. Those messengers might kill pain,  trigger a cell to grow or turn on the immune system to repel an invader.  

In a sentence

Scientists are studying peptides from frogs to see if they can be used to help people fight infections.

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Bethany Brookshire was a longtime staff writer at Science News Explores and is the author of the book Pests: How Humans Create Animal Villains. She has a Ph.D. in physiology and pharmacology and likes to write about neuroscience, biology, climate and more. She thinks Porgs are an invasive species.

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