Colloid

In general, a colloid or colloidal dispersion is a two-phase system of matter; a type of mixture intermediate between homogeneous mixtures and heterogeneous mixtures.

Colloids in biology

In the early 20th century, before enzymology was well understood, colloids were thought to be the key to the operation of enzymes; i.e., the addition of small quantities of an enzyme to a quantity of water would, in some fashion yet to be specified, subtly alter the properties of the water so that it would break down the enzyme's specific substrate, such as a solution of ATPase breaking down ATP. Furthermore, life itself was explainable in terms of the aggregate properties of all the colloidal substances that make up an organism. As more detailed knowledge of biology and biochemistry developed, of course, the colloidal theory was replaced by the macromolecular theory, which explains an enzyme as a collection of identical huge molecules which act as very tiny machines, freely moving about between the water molecules of the solution and individually operating on the substrate, no more mysterious than a factory full of machinery. The properties of the water in the solution are not altered, other than the simple osmotic changes that would be caused by the presence of any solute.

Related Topics:
20th century - Enzymology - Enzyme - Substrate - ATPase - ATP - Life - Aggregate - Organism - Biology - Biochemistry - Macromolecular - Molecule - Machine - Factory - Osmotic - Solute

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