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Home > Library > Literature & Language > Dictionaryn.
A very large molecule, such as a polymer or protein, consisting of many smaller structural units linked together. Also called supermolecule.
macromolecular mac'ro·mo·lec'u·lar (-mə-lĕk'yə-lər) adj.
Chemistry Dictionary: macromolecule
Top Home > Library > Science > Chemistry DictionaryA very large molecule. Natural and synthetic polymers have macromolecules, as do such substances as haemoglobin. See also colloids.
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Dental Dictionary: macromolecule
Top Home > Library > Health > Dental Dictionary
n
Any substance with molecules of colloidal size, notably proteins, nucleic acids, and polysaccharides.
Britannica Concise Encyclopedia: macromolecule
Top Home > Library > Miscellaneous > Britannica Concise Encyclopedia
Any very large molecule, composed of much larger numbers (hundreds or thousands) of atoms than ordinary molecules. Some macromolecules are individual entities that cannot be subdivided without losing their identity (e.g., certain proteins, with molecular weights into the millions). Others (polymers) are multiples of a repeating building block (monomer) in chains or networks (e.g., plastics, cellulose). Most macromolecules are in the size range typical of colloids.
For more information on macromolecule, visit Britannica.com.
Columbia Encyclopedia: macromolecule
Top Home > Library > Miscellaneous > Columbia Encyclopediamacromolecule, term that may refer either to a crystal such as a diamond, in which the atoms are identical and held by covalent bonds (see chemical bond) of equal strength, or to one of the units that compose a polymer. Macromolecules such as proteins and nucleic acids are vital to the functions of living cells.
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Veterinary Dictionary: macromolecule
Top Home > Library > Animal Life > Veterinary DictionaryA very large molecule having a polymeric chain structure, as in proteins, polysaccharides, etc.
Wikipedia: Macromolecule
Top Home > Library > Miscellaneous > WikipediaThis article is about a macromolecule. For the scientific journal Macromolecules, see Macromolecules Journal.
Illustration of a polypeptide macromoleculeThe term macromolecule by definition implies "large molecule". In the context of biochemistry, the term may be applied to the four conventional biopolymers (nucleic acids, proteins, carbohydrates, and lipids), as well as non-polymeric molecules with large molecular mass such as macrocycles. Macromolecules are synthesized through the process of polymerization, during which monomers (mono=single, meros=part) are assembled into large molecules - macromolecules.
Contents [hide]
1 Usage
2 Properties
3 References
4 External links
Usage
The term macromolecule was coined by Nobel laureate Hermann Staudinger in the 1920s although his first relevant publication on this field only mentions high molecular compounds (in excess of 1000 atoms). [1]. At that time the phrase polymer as introduced by Berzelius in 1833 had a different meaning from that of today: it simply was another form of isomerism for example with benzene and acetylene and had little to do with size [2].
Usage of the term to describe different forms of large molecules varies among the disciplines. For example, while biology refers to macromolecules as the four large molecules living things are composed of, from the perspective of chemistry, the term may refer to aggregates of two or more macromolecules held together by intermolecular forces rather than covalent bonds but which do not readily dissociate.[3]
According to the recommended IUPAC definition, the term macromolecule as used in polymer science refers only to a single molecule. For example, a single polymeric molecule is appropriately described as a "macromolecule" or "polymer molecule" rather than a "polymer", which suggests a substance composed of macromolecules.[4]
Structure of a polyphenylene dendrimer macromolecule reported by Müllen,k and coworkers in Chem.-Eur. J., 2002, 3858-3864.Because of their size, macromolecules are not conveniently described in terms of stoichiometry alone. The structure of simple macromolecules, such as homopolymers, may be described in terms of the individual monomer subunit and total molecular mass. Complicated biomacromolecules, on the other hand, require multi-faceted structural description such as the hierarchy of structures used to describe proteins.
Properties
Substances that are composed macromolecules often have unusual physical properties. Although too small to see, individual pieces of DNA in solution can be broken in two simply by suctioning the solution through an ordinary straw. This is not true of smaller molecules. The 1964 edition of Linus Pauling's College Chemistry asserted that DNA in nature is never longer than about 5000 base pairs. This is because biochemists were inadvertently and consistently breaking their samples into pieces. In fact, the DNA of chromosomes can be hundreds of millions of base pairs long.
Another common macromolecular property that does not characterize smaller molecules is the need for assistance in dissolving into solution. Many require salts or particular ions to dissolve in water. Proteins will denature if the solute concentration of their solution is too high or too low.
High concentrations of macromolecules in a solution can alter the rates and equilibrium constants of the reactions of other macromolecules, through an effect known as macromolecular crowding.[5] This comes from macromolecules excluding other molecules from a large part of the volume of the solution, thereby increasing these molecules' effective concentration.
References
^ Staudinger, H.; Fritschi, J. Über die Hydrierung des Kautschuks und über seine Konstitution. Helv. Chim. Acta 1922, 5, 785–806.
^ The Origin of the Polymer Concept by William B. Jensen Journal of Chemical Education • Vol. 85 No. 5 May 624 2008
^ van Holde, K.E. Principles of Physical Biochemistry Prentice Hall: New Jersey, 1998
^ http://www.iupac.org/reports/1996/6812jenkins/6812basicterms.pdf
^ Minton AP (July 2006). "How can biochemical reactions within cells differ from those in test tubes?". J. Cell. Sci. 119 (Pt 14): 2863–9. doi:10.1242/jcs.03063. PMID 16825427. http://jcs.biologists.org/cgi/content/full/119/14/2863.
External links
Synopsis of Chapter 5, Campbell & Reece, 2002
Lecture notes on the structure and function of macromolecules
Several (free) introductory macromolecule related internet-based courses
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Dictionary. The American Heritage® Dictionary of the English Language, Fourth Edition Copyright © 2007, 2000 by Houghton Mifflin Company. Updated in 2007. Published by Houghton Mifflin Company. All rights reserved. Read more
Chemistry Dictionary. A Dictionary of Chemistry. Sixth Edition. Copyright © Market House Books Ltd, 2008. All rights reserved. Read more
Dental Dictionary. Mosby's Dental Dictionary. Copyright © 2004 by Elsevier, Inc. All rights reserved. Read more
Britannica Concise Encyclopedia. Britannica Concise Encyclopedia. © 2006 Encyclopædia Britannica, Inc. All rights reserved. Read more
Columbia Encyclopedia. The Columbia Electronic Encyclopedia, Sixth Edition Copyright © 2003, Columbia University Press. Licensed from Columbia University Press. All rights reserved. www.cc.columbia.edu/cu/cup/ Read more
Veterinary Dictionary. Saunders Comprehensive Veterinary Dictionary 3rd Edition. Copyright © 2007 by D.C. Blood, V.P. Studdert and C.C. Gay, Elsevier. All rights reserved. Read more
Wikipedia. This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Macromolecule". Read more
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