Scientists Say	Chemistry
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.
ibreakstock/iStockphoto
By Bethany Brookshire
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.
Scientists are studying peptides from frogs to see if they can be used to help people fight infections.
Check out the full list of Scientists Say here.
amino acids Simple molecules that occur naturally in plant and animal tissues and that are the basic building blocks of proteins.
bacteria (singular: bacterium) Single-celled organisms. These dwell nearly everywhere on Earth, from the bottom of the sea to inside other living organisms (such as plants and animals).
germ Any one-celled microorganism, such as a bacterium or fungal species, or a virus particle. Some germs cause disease. Others can promote the health of more complex organisms, including birds and mammals. The health effects of most germs, however, remain unknown.
infection A disease that can spread from one organism to another. It's usually caused by some type of germ.
molecule An electrically neutral group of atoms that represents the smallest possible amount of a chemical compound. Molecules can be made of single types of atoms or of different types. For example, the oxygen in the air is made of two oxygen atoms (O2), but water is made of two hydrogen atoms and one oxygen atom (H2O).
organism Any living thing, from elephants and plants to bacteria and other types of single-celled life.
peptide A short chain of amino acids (usually fewer than 100).
protein A compound made from one or more long chains of amino acids. Proteins are an essential part of all living organisms. They form the basis of living cells, muscle and tissues; they also do the work inside of cells. Among the better-known, stand-alone proteins are the hemoglobin (in blood) and the antibodies (also in blood) that attempt to fight infections. Medicines frequently work by latching onto proteins.
About Bethany Brookshire
Bethany is the staff writer at Science News for Students. She has a Ph.D. in physiology and pharmacology from Wake Forest University School of Medicine.
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