chain

1. In chemistry, a series of atoms held together by one or more covalent bonds. 2. In bacteriology, a linear arrangement of living cells that have divided in one plane and remain attached to each other. 3. A series of reactions. 4. In anatomy, a linked series of structures, e.g., ossicular c., c. ganglia, under ganglion. SEE ALSO: sympathetic trunk. [L. catena]

- A c. 1. the shorter polypeptide component of insulin containing 21 amino acyl residues, beginning with a glycyl residue (NH₂-terminus); insulin is formed by the linkage of an A c. to a B c. by two disulfide bonds; the amino-acid composition of the A c. is a function of species; 2. in general, one of the polypeptides in a multiprotein complex.

- B c. 1. the longer polypeptide component of insulin containing 30 amino acyl residues, beginning with a phenylalanyl residue (NH₂-terminus); insulin is formed by the linkage of a B c. to an A c. by two disulfide bonds; the amino acid composition of the B c. is a function of species; 2. the light c. of an immunoglobulin.

- behavior c. related behaviors in a series in which each response serves as a stimulus for the next response.

- C c. SYN: C-peptide.

- cold c. a system of protection against high environmental temperatures for heat-labile vaccines, sera, and other biological preparations.

- electron-transport c. SYN: respiratory c..

- ganglionic c. SYN: sympathetic trunk.

- heavy c. a polypeptide c. of high molecular weight (about 400–500 amino acyl residues), as the γ, α, μ, δ, or ε chains in immunoglobulin, determining the immunoglobulin class and subclass. This c. also determines if complement can be bound and if the c. can pass through the placenta. There are two identical chains in each immunoglobulin. SYN: H c..

- J c. a glycopeptide, cysteine-rich polypeptide that is bonded to polymeric IgA and IgM; its function is to ensure correct polymerization of the subunits of IgA and IgM and to be secreted externally. [joining c.]

- L c. SYN: light c..

- light c. a polypeptide c. of low molecular weight (about 200 amino acyl residues), as the κ or λ chains in immunoglobulin. There are two identical light chains in each immunoglobulin monomer. SYN: L c..

- long c. in bacteriology, a continuous line of more than eight cells.

- ossicular c. SYN: auditory ossicles, under ossicle.

- respiratory c. a sequence of energy-liberating oxidation-reduction reactions whereby electrons are accepted from reduced compounds and eventually transferred to oxygen with the formation of water. SYN: cytochrome system, electron-transport c., electron-transport system.

- short c. in bacteriology, a string of two to eight cells.

- side c. 1. a c. of noncyclic atoms linked to a benzene ring, or to any cyclic c. compound; 2. the atoms of an α-amino acid other than the α-carboxyl group, the α-amino group, the α-carbon, and the hydrogen attached to the α-carbon.

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chain 'chān n, often attrib

1) a series of things (as bacteria) linked, connected, or associated together

2) a number of atoms or chemical groups united like links in a chain

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(chān) 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.