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Monomers are small, individual subunits, often built of hydrocarbons, that join together to form polymers.


Each monomer molecules looks very different, but they do have some common features.
Actually, the monomers have two distinctive features
  • carbon-carbon double bonds and
  • side groups
The highlighted areas show the side groups on these monomer molecules. These groups give the polymer chain some of its properties.

The double bond, however, is the vital feature that allows these monomers to form the long polymer chains.
One example of the carboxylic acid group


R means the "Rest" of the molecule.
Two examples of monomers that contain the functional group

Two other functional groups seen in polymerization reactions are the amine group,
, and the alcohol group,.
Below are examples of monomers containing the functional group

Notice that each of these monomers contains two functional groups. That is, they are difunctional. It is their difunctionality that allows the monomers to form long polymer chains.
The first group of monomers had
  • carbon-carbon double bonds and
  • side groups
The second group of monomers had
  • functional groups and
  • two functional groups each (that is, they are difunctional)


Poly- means "many".

Polymer means many monomers. Sometimes polymers are also known as macromolecules or large-sized molecules. Usually, polymers are organic.

A monomer is a molecule that can bond in long chains.

Here is a monomer: 
Here is a polymer:  

A polymer is the long chain that gives polymers their unique properties. Consider ethane, CH3-CH3, which is a gas molecule at room temperature. Because of their small size, ethane molecules are very mobile and can run almost anywhere they want without interacting with other molecules. Now, if we double the chain length or the total number of carbons to four, we get butane, CH3-CH2-CH2-CH3, which is a liquid fuel. In liquids, atoms or molecules can no longer act as independent units. Because of their larger size, butane molecules are less mobile than ethane molecules. Their lowered mobility allows them to run into or interact with one another more frequently. When the chain length increases 6 fold, as in paraffin, CH3(CH2CH2)10CH3, we get a waxy substance. In this case, the solid-like property of paraffin is a reflection of the entanglement of its long molecules when they move. If we keep increasing the number of repeating carbon units to, say, 2000, i.e., CH3(CH2CH2)2000CH3, we have a polyethylene polymer, which is a very strong, brittle solid. The polymer molecules have become so long and so entangled that their movement becomes almost completely restricted. At this point, they appear to be attached to other molecules, which act as "permanent" neighbours.




2 C atoms




4 C atoms




22 C atoms




4002 C atoms


Monomers link together by two basic methods
  • Addition polymerization and
  • Condensation polymerization

Nature of Bond Linking

In a polypeptide or a protein, amino acids are linked by a peptide bond which is formed when the carboxyl (-COOH) group of one amino acid reacts with the amino (-NH2) group of the next amino acid with the elimination of water moiety. This process is called dehydration.

In polysaccharide, the individual monosaccharides are linked by a glycosidic bond. This bond is also formed by dehydration. This bond is formed between two carbon atoms of two adjacent monosaccharides.

In a nucleic acid, a phosphate moiety links the 3'-carbon of one sugar of one nucleotide to the 5'-carbon of the sugar of the succeeding nucleotide. The bond between the phosphate and hydroxyl group of sugar is an ester bond. As there is one ester bond on either side, it is called phosphodiester bond. Nucleic acids exhibit a wide variety of secondary structures.

The nitrogen bases are projected more or less perpendicular to this backbone, but face inside in the DNA. A and G of one strand pairs on the other strand with T and C. There are two hydrogen bonds between A and T. There are three hydrogen bonds between G and C.


(http://academic.brooklyn.cuny.edu/biology/bio4fv/page/molecular biology/dna-structure.html)

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