Also found in: Dictionary, Thesaurus, Legal, Financial, Acronyms, Idioms, Encyclopedia, Wikipedia.
a collection of objects linked together in linear fashion, or end to end, as the assemblage of atoms or radicals in a chemical compound, or an assemblage of individual bacterial cells.
branched chain an open chain of atoms, usually carbon, with one or more side chains attached to it.
closed chain several atoms linked together so as to form a ring, which may be saturated, as in cyclopentane, or aromatic, as in benzene.
H chain (heavy chain) any of the large polypeptide chains of five classes that, paired with the L or light chains, make up the antibody molecule of an immunoglobulin; heavy chains bear the antigenic determinants that differentiate the classes of immunoglobulins. See also heavy chain disease.
J chain a polypeptide occurring in polymeric IgM and IgA molecules.
L chain (light chain) either of the two small polypeptide chains (molecular weight 22,000) that, when linked to H or heavy chains by disulfide bonds, make up the antibody molecule of an immunoglobulin monomer; they are of two types, kappa and lambda, which are unrelated to immunoglobulin class differences.
open chain a series of atoms united in a straight line; components of this series are related to methane.
chain reaction a chemical reaction that is self-propagating; each time a free radical is destroyed a new one is formed.
side chain a group of atoms attached to a larger chain or to a ring.
1 (in chemistry) a reaction that proceeds through one or more reactive intermediates; one of the required reactive intermediates (usually free radicals) is formed in each step of the reaction. Examples include the polymerization of organic monomers into plastics or in the free radical halogenation of hydrocarbons.
2 (in physics) a reaction that perpetuates itself by the proliferating fission of nuclei and the release of atomic particles that cause more nuclear fissions.
chain re·ac·tion(chān rē-ak'shŭn)
A self-perpetuating reaction in which a product of one step in the reaction itself serves to bring about the next step in the reaction, and so on.
chain reactionA self-sustaining reaction maintained by producing products that induce it. Neutrons produced by atomic fission in a mass of uranium can induce sustainable further fission of uranium atoms.
chain reactiona chemical or atomic reaction in which the products of each state promote a subsequent reaction. Initially there is a slow induction period, but as the reaction progresses the reaction rate is accelerated.
1. opposite action or counteraction; the response of a part to stimulation.
2. the phenomena caused by the action of chemical agents; a chemical process in which one substance is transformed into another substance or substances.
one which is self-propagating; a chemical process in which each time a free radical is destroyed a new one is formed.
one in which the free energy released by one chemical reaction drives the other reaction.
photosynthetic reaction which fixes CO2 into sugar and which occurs without exposure to light. Called also Calvin cycle.
reaction of degeneration
the reaction to electrical stimulation of muscles whose nerves have degenerated, consisting of loss of response to a faradic stimulation in a muscle, and to galvanic and faradic stimulation in the nerve.
a reaction, such as an allergic reaction, occurring hours to days after exposure to an inducer.
false negative reaction
an erroneously negative reaction to a test.
false positive reaction
an erroneously positive reaction to a test.
first set reaction
2. formation of a papule and areola without development of a vesicle following smallpox vaccination.
reflex elongation of extensor muscles that permits flexion of a limb.
leukemic reaction, leukemoid reaction
a peripheral blood picture resembling leukemia or indistinguishable from it on the basis of morphological appearance alone, characterized by immature leukocytes in the blood.
reaction pattern analysis
designed to replace archaic, non-specific descriptions of the reactions of the skin to noxious influences; recommended categories are (1) perivascular dermatitis, (2) interface dermatitis, (3) vasculitis, (4) nodular and diffuse dermatitis, (5) intradermal vesicular and pustular dermatitis, (6) subepidermal vesicular and pustular dermatitis, (7) perifolliculitis, folliculitis and furunculosis, (8) fibrosing dermatitis, (9) panniculitis, (10) atrophic dermatosis, (11) mixed reaction patterns.
second set reaction
lack of production of by-products in enzymatic reactions with yields of products being nearly 100%.
development of suppurative peritonitis, localized to the scrotal sac, in the guinea pig after the intraperitoneal injection of material containing Burkholderia mallei.
1. alarm reaction.
2. gross stress reaction.
the time elapsing between the application of a stimulus and the resulting reaction.
a cutaneous sensitivity rection to skin injury or administration of antigen, due to histamine production and marked by edematous elevation and erythematous flare.