Molecule
The smallest unit of a substance that can exist alone and retain the character of that substance.
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The smallest possible quantity of a di-, tri-, or polyatomic substance that retains the chemical properties of the substance. [Mod. L. molecula, dim. of L. moles, mass]
- accessory molecules cell surface adhesion molecules on T cells that are involved in binding of one cell to another cell activation, and in signal transduction, e.g., CD4.
- adhesion molecules molecules that are involved in T helper-accessory cell, T helper-B cell, and T cytotoxic-target cell interactions; extracellular matrix proteins that attract leukocytes from the circulation.
- cell adhesion m. (CAM) proteins that hold cells together, e.g., uvomorulin, and hold them to their substrates, e.g., laminin.
- chimeric m. a m. (usually a biopolymer) containing sequences derived from two different genes; specifically, from two different species. Cf.:chimera.
- class I m. a major histocompatibility complex antigen made up of two noncovalently bonded polypeptide chains, one glycosylated, heavy, and variable with antigen specificity; the other chain is β2-microglobulin.
- class II m. a major histocompatibility complex membrane-piercing antigen made up of two noncovalently bonded polypeptide chains designated α and β.
- costimulatory m. membrane-bound or secreted product of accessory cells that is required for signal transduction.
- endothelial-leukocyte adhesion m. (E-LAM) a glycoprotein on the surface of endothelial cells that is involved in blood leukocyte attachment to vessel walls as well as emigration from the vessels into the tissues.
- gram-m. the amount of a substance with a mass in grams equal to its molecular weight; e.g., a gram-m. of hydrogen weighs 2.016 g, that of water 18.015 g.
- intercellular adhesion m.-1 (ICAM-1) a glycoprotein that is expressed on a variety of cells. It is the ligand for LFA-1 as well as the receptor for the rhinoviruses.
- lectin pathway m. the binding of mannose-binding protein to bacterial carbohydrates resulting in activation of the complement pathway.

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mol·e·cule 'mäl-i-.kyü(ə)l n the smallest particle of a substance that retains all the properties of the substance and is composed of one or more atoms

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mol·e·cule (molґə-kūl) [L. molecula little mass] a very small mass of matter; the smallest amount of a substance which can exist alone; an aggregation of atoms; specifically, a chemical combination of two or more atoms which form a specific chemical substance. To break up the molecule into its constituent atoms is to change its character. The number and kind of atoms in a molecule vary with the compound. molecular adj

Medical dictionary. 2011.

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  • MOLÉCULE — Le terme «molécule» est un concept opératoire fondamental de la pensée réductionniste. C’est un objet théorique au moyen duquel on peut dire, paraphrasant Jean Perrin, que le visible complexe de la matière se trouve représenté par de l’invisible… …   Encyclopédie Universelle

  • Molecule — Molécule Représentation 3D d une molécule de saccharose. Une molécule est un assemblage d atomes dont la composition est donnée par sa formule chimique. Le nom molécule provient du nom latin molecula, diminutif du nom latin moles, se traduisant… …   Wikipédia en Français

  • Molecule — Mol e*cule, n. [Dim. fr. L. moles a mass: cf. F. mol[ e]cule. See 3d {Mole}.] 1. One of the very small invisible particles of which all ordinary matter is supposed to consist. [1913 Webster] 2. (Physics) The smallest part of any substance which… …   The Collaborative International Dictionary of English

  • molecule — (n.) 1794, extremely minute particle, from Fr. molécule (1670s), from Mod.L. molecula, dim. of L. moles mass, barrier (see MOLE (Cf. mole) (3)). A vague meaning at first; the vogue for the word (used until late 18c. only in Latin form) can be… …   Etymology dictionary

  • molecule — [mäl′ə kyo͞ol΄] n. [Fr molécule < ModL molecula, dim. of L moles, a mass: see MOLE3] 1. the smallest particle of an element or compound that can exist in the free state and still retain the characteristics of the element or compound: the… …   English World dictionary

  • molecule — atom, *particle, corpuscle …   New Dictionary of Synonyms

  • molecule — [n] smallest part bit, fragment, iota, jot, minim, mite, modicum, mote, ounce, particle, ray, speck, unit; concepts 393,831 …   New thesaurus

  • molecule — ► NOUN ▪ a group of atoms chemically bonded together, representing the smallest fundamental unit of a compound that can take part in a chemical reaction. ORIGIN French, from Latin molecula small mass , from moles mass …   English terms dictionary

  • Molécule — Représentation schématique 3D d une molécule de saccharose …   Wikipédia en Français

  • Molecule — 3D (left and center) and 2D (right) representations of the terpenoid molecule atisane A molecule (pronounced  …   Wikipedia

  • molecule — /mol euh kyoohl /, n. 1. Chem., Physics. the smallest physical unit of an element or compound, consisting of one or more like atoms in an element and two or more different atoms in a compound. 2. Chem. a quantity of a substance, the weight of… …   Universalium

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