Scientists Say: Peptide | Science News for Students

Scientists Say: Peptide

These tiny chemical chains are the building blocks of proteins and more
Sep 17, 2018 — 6:30 am EST
protein structure

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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Power Words

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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).

cell     The smallest structural and functional unit of an organism. Typically too small to see with the unaided eye, it consists of a watery fluid surrounded by a membrane or wall. Depending on their size, animals are made of anywhere from thousands to trillions of cells. Most organisms, such as yeasts, molds, bacteria and some algae, are composed of only one cell.

chemical     A substance formed from two or more atoms that unite (bond) in a fixed proportion and structure. For example, water is a chemical made when two hydrogen atoms bond to one oxygen atom. Its chemical formula is H2O. Chemical also can be an adjective to describe properties of materials that are the result of various reactions between different compounds.

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.