A monomer (// MON-ə-mər) (mono-, "one" + -mer, "part") is a molecule that may bind chemically to other molecules to form a polymer. The term "monomeric protein" may also be used to describe one of the proteins making up a multiprotein complex. The most common natural monomer is glucose, which is linked by glycosidic bonds into polymers such as cellulose, starch, and glycogen. Most often the term monomer refers to the organic molecules which form synthetic polymers, such as vinyl chloride, which is used to produce the polymer polyvinyl chloride (PVC).The process by which monomers combine end to end to form a polymer is called polymerization. Molecules made of a small number of monomer units, up to a few dozen, are called oligomers.
Amino acids are natural monomers that polymerize at ribosomes to form proteins. Nucleotides, monomers found in the cell nucleus, polymerize to form nucleic acids – DNA and RNA. Glucose monomers can polymerize to form starches, glycogen or cellulose; xylose monomers can polymerise to form xylan. In all these cases and is thus not pliable, a hydrogen atom and a hydroxyl (-OH) group are lost to form H2O, and an oxygen atom links each monomer unit. Due to the formation of water as one of the products, these reactions are known as dehydration.
The lower molecular weight compounds built from monomers are also referred to as dimers, trimers, tetramers, pentamers, hexamers, heptamers, octamers, nonamers, decamers, dodecamers, eicosamers, etc. if they have 2, 3, 4, 5, 6, 7, 8, 9, 10, 12, or 20 monomer units, respectively. Any number of these monomer units may be indicated by the appropriate Greek prefix. Larger numbers are often stated in English or numbers instead of Greek; e.g., a 20-mer is formed from 20 monomers. Molecules made of a small number of monomer units, up to a few dozen, are called oligomers.
In the light of the current[when?] tight monomers market, particularly in propylene, and of the benefits of membrane-based recovery processes, major polyolefin producers around the world already employ such recovery processes in new state-of-the-art plants. In order to enhance the competitiveness of older plants, the use of a recovery solution has started to become mandatory.[dead link]
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