Everything about Macromolecules totally explained
The term
macromolecule by definition implies "large
molecule". In the context of
biochemistry, the term may be applied to the four conventional
biopolymers (
nucleotides,
proteins,
carbohydrates, and
lipids), as well as non-polymeric molecules with large molecular mass such as
macrocycles.
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). . 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 .
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 don't readily dissociate.
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.
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 of 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 isn't 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 tens of millions of base pairs long.
Another common macromolecular property that doesn't 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.
Further Information
Get more info on 'Macromolecules'.
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