Monomer Definition

A monomer is a small molecule that reacts with a similar molecule to form a larger molecule. It is the smallest unit in a polymer, which is often a macromolecule with high molecular weight.

Monomers are the building blocks for biological macromolecules such as DNA, RNA, proteins and carbohydrates. At the end of digestion, these polymers are broken down into their monomeric components – carbohydrates are enzymatically digested to monosaccharides, DNA and RNA are converted into nucleotides, proteins are broken down into their constituent amino acids, before being absorbed by the body. These nutrients are then used to create polymers based on the genetic composition and instructions within the body.

Monomers are also important in the synthesis of many materials in the industrial world. Polymerization of ethane results in the creation of polyethane – the most common plastic in the world. Many synthetic fabrics are also polymers created usually from two alternating monomers.

The word monomer derives from the Greek prefix monos – which means “single” or “only.”

Examples of Monomer

Monosaccharides – The Most Accessible Energy

Carbohydrates are macronutrient polymers that must be broken into smaller units, called monosaccharides, before being used for energy. Monosaccharides, along with glucose and fructose, are part of a larger group of isomers.

Monosaccharides typically only form bonds with other monosaccharides, and are released into the body through a process called glycolysis. Glycolysis is the only process needed to break down carbohydrates to turn them into energy, making monosaccharides the most readily-accessible form of energy.

Fatty Acids – A Multi-Step Process

Fatty acids cannot be directly oxidized to provide energy unlike monosaccharides. The bonds in fatty acids require three processes to before energy is released. During the first process, lipolysis, fats stored in the body’s adipose tissue are mobilized. From there, they undergo activation, during which they move to peroxisomes and the mitochondria. These organelles then oxidize the fatty substances, isolating fatty acids for energy.

Fatty acids, like monosaccharides, are monomers that, absorbed through food, provide energy to the body. However, as shown by the more intense process that fatty acids undergo, monomers rely on several diverse paths for polymerization.


As shown by fatty acids in Example #2, monomers do not form exclusive bonds even though their basic definition signifies a bond between numerous units. Typically, they bond with other monomers to create larger units.

Silicone, a sealing material used in construction and electronics, is an example. This material, also called polysiloxanes, consists primarily of alternating silicon atom monomers and oxygen atom monomers. However, when paired with carbon monomers and/or hydrogen monomers, it becomes more resistant, more durable, and less combustible.

From this comes evidence that monomers, while able to create “pure” polymers, can also be combined with other isomers to create materials that do not occur in nature.

Related Biology Terms

  • Polymer – Also known as a macromolecule, a molecule that results from the pairing of one or more monomers.
  • Isomer – A monomer or chemical compound that has the same chemical formula as other monomers or chemical compounds, but a different number of electrons.


1. Monomers are the smallest unit of:
A. A polymer
B. A macromolecule
C. An isomer
D. Both A and B

Answer to Question #1

2. Monomers are ________, but some monomers take a longer process to isolate than others.
A. Micellar
B. Wine cellar
C. Unicellular
D. Unicyclical

Answer to Question #2

3. Monomers sometimes exist as isomers, which means:
A. They have a different chemical compound than any other existing monomer.
B. They have the same chemical formula as other monomers.
C. The have the same chemical compound as other monomers.
D. They cannot bond with any other monomer.

Answer to Question #3

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