| Victor-Michaelis-Menten equation | <chemistry> Equation derived from a simple kinetic model for a single-substrate non-cooperative enzyme-catalyzed reaction that successfully accounts for the hyperbolic adsorption isotherm) relationship between substrate concentration and reaction rate. V = Vmax x S/(S + Km), where V is the initial velocity of the reaction, Km is the Michaelis constant, Vmax is the maximum rate approached by very high substrate concentrations and S is the initial substrate concentration. Similar equations can be derived for conditions in which the product is present and for multisubstrate enzymes. Synonym: Victor-Michaelis-Menten equation. (12 Jul 2000) |
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| Michaelis complex | Binary complex of an enzyme. (05 Mar 2000) |
| Michaelis constant | <chemistry> The true dissociation constant for the enzyme-substrate binary complex in a single-substrate rapid equilibrium enzyme-catalyzed reaction (usually symbolised by Ks), the concentration of the substrate at which half the true maximum velocity of an enzyme-catalyzed reaction is achieved (when velocities are measured under initial rate and steady state conditions). The ratio of rate constants (k2 + k3)/k1 in the single-substrate enzyme-catalyzed reaction: E + S &dblarr; ES &dblarr; E + products where E represents the free enzyme, S is the substrate, and ES is the central binary complex. The expression for the Michaelis constant will be more complex for multisubstrate reactions. An apparent Michaelis constant is a constant determined either under conditions that are not strictly steady state and initial rate or one that varies with the concentration of one or more cosubstrates. See: Michaelis-Menten equation. Synonym: Michaelis-Menten constant. (05 Mar 2000) |
| Michaelis-Gutmann body | <radiology> A rounded homogenous or concentrically laminated body, 1 to 10 u in diameter, containing calcium apatite and iron; found within macrophages in the bladder wall in malakoplakia. (12 Jul 2000) |
| Michaelis, Leonor | <person> German-U.S. Chemist, 1875-1949. See: Michaelis-Gutmann body, Michaelis constant, Michaelis-Menten constant, Michaelis-Menten equation, Michaelis-Menten hypothesis. (05 Mar 2000) |
| Michaelis-Menten constant | <chemistry> The true dissociation constant for the enzyme-substrate binary complex in a single-substrate rapid equilibrium enzyme-catalyzed reaction (usually symbolised by Ks), the concentration of the substrate at which half the true maximum velocity of an enzyme-catalyzed reaction is achieved (when velocities are measured under initial rate and steady state conditions). The ratio of rate constants (k2 + k3)/k1 in the single-substrate enzyme-catalyzed reaction: E + S &dblarr; ES &dblarr; E + products where E represents the free enzyme, S is the substrate, and ES is the central binary complex. The expression for the Michaelis constant will be more complex for multisubstrate reactions. An apparent Michaelis constant is a constant determined either under conditions that are not strictly steady state and initial rate or one that varies with the concentration of one or more cosubstrates. See: Michaelis-Menten equation. Synonym: Michaelis-Menten constant. (05 Mar 2000) |
| Michaelis-Menten equation | <chemistry> Equation derived from a simple kinetic model for a single-substrate non-cooperative enzyme-catalyzed reaction that successfully accounts for the hyperbolic adsorption isotherm) relationship between substrate concentration and reaction rate. V = Vmax x S/(S + Km), where V is the initial velocity of the reaction, Km is the Michaelis constant, Vmax is the maximum rate approached by very high substrate concentrations and S is the initial substrate concentration. Similar equations can be derived for conditions in which the product is present and for multisubstrate enzymes. Synonym: Victor-Michaelis-Menten equation. (12 Jul 2000) |
| Michaelis-Menten hypothesis | <chemistry> That a complex is formed between an enzyme and its substrate (the O'Sullivan-Tompson hypothesis), which complex then decomposes to yield free enzyme and the reaction products (Brown hypothesis), the latter rate determining the overall rate of substrate-product conversion. See: Michaelis-Menten constant, Michaelis-Menten equation. (05 Mar 2000) |
| rhomboid | <geometry> Quadangular, with the lateral angles obtuse. (23 Aug 1998) |
| rhomboid fossa | The floor of the fourth ventricle of the brain, formed by the ventricular surface of the rhombencephalon. Synonym: fossa rhomboidea. (05 Mar 2000) |
| rhomboid impression | <anatomy> An irregular pitted area on the inferior surface of the clavicle at its sternal end, giving attachment to the costoclavicular ligament. Synonym: impressio ligamenti costoclavicularis, costal tuberosity, rhomboid impression, tuberositas costalis. (05 Mar 2000) |
| rhomboid ligament | <anatomy> The ligament that connects the first rib and the clavicle near its sternal end; limits elavation of shoulder (at sternoclavicular joint). Synonym: ligamentum costoclaviculare, rhomboid ligament. (05 Mar 2000) |
| rhomboid minor | <anatomy, muscle> Origin, spinous processes of sixth and seventh cervical vertebrae; insertion, medial margin of scapula above spine; action, draws scapula toward vertebral column and slightly upward; nerve supply, dorsal nerve of scapula. Synonym: musculus rhomboideus minor, lesser rhomboid muscle. (05 Mar 2000) |
| greater rhomboid muscle | <anatomy, muscle> Origin, spinous processes and corresponding supraspinous ligaments of first four thoracic vertebrae; insertion, medial border of scapula below spine; action, draws scapula toward vertebral column; nerve supply, dorsal of scapula nerve. Synonym: musculus rhomboideus major, greater rhomboid muscle. (05 Mar 2000) |
| nerve to rhomboid | <anatomy, nerve> Arises from ventral primary rami of the fifth to seventh cervical nerves and passes downward to supply the levator scapulae and the rhomboideus major and minor muscles. Synonym: nervus dorsalis scapulae, dorsal nerve of scapula, nerve to rhomboid, posterior scapular nerve. (05 Mar 2000) |