| hydrogen ion | A hydrogen atom minus its electron and therefore carrying a unit positive charge (i.e., a proton); in water, it combines with a water molecule to form hydronium ion, H3O+. (05 Mar 2000) |
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| hydrogen number | The quantity of hydrogen that 1 g of fat will absorb; it is a measurement of the amount of unsaturated fatty acids in the fat. See: iodine number. (05 Mar 2000) |
| hydrogen peroxide | <chemical> Hydrogen peroxide is produced by vertebrate phagocytes and is used in bacterial killing (the myeloperoxidase halide system). (05 May 1997) |
| hydrogen phosphide | <chemistry> A colourless gas, PH3, analogous to ammonia, and having a disagreeable odour resembling that of garlic. Synonym: hydrogen phosphide, and formerly, phosphureted hydrogen. It is the most important compound of phosphorus and hydrogen, and is produced by the action of caustic potash on phosphorus. It is spontaneously inflammable, owing to impurities, and in burning produces peculiar vortical rings of smoke. Source: Websters Dictionary (01 Mar 1998) |
| hydrogen-potassium-exchanging atpase | <enzyme> An enzyme isolated from the gastric mucosa that catalyses the hydrolysis of ATP coupled with the exchange of hydrogen and potassium ions across the cell wall. Chemical name: ATP phosphohydrolase (H+/K+-transporting) Registry number: EC 3.6.1.36 (12 Dec 1998) |
| hydrogen pump | Molecular mechanism for acid secretion from gastric parietal cells based on the activity of a H+-K+-ATPase. (05 Mar 2000) |
| hydrogen sulfide | <chemical> Hydrogen sulfide (h2s). A flammable, poisonous gas with a characteristic odour of rotten eggs. It is used in the manufacture of chemicals, in metallurgy, and as an analytical reagent. Chemical name: Hydrogen sulfide (H2S) (12 Dec 1998) |
| hydrogen transport | The transfer of hydrogen from one metabolite (hydrogen donor) to another (hydrogen acceptor) through the action of an enzyme system; the donor is thus oxidised and the acceptor reduced. (05 Mar 2000) |
| hydrogen-transporting ATP synthase | <enzyme> A group of enzymes which are involved in the reversible synthesis of ATP and that transport protons from the cytoplasmic to the matrix side of the mitochondrial membrane. The flow of protons through the f(0) channel results in ATP synthesis by f1. Chemical name: ATP phosphohydrolase (H+-transporting) Registry number: EC 3.6.1.34 (12 Dec 1998) |
| sulfureted hydrogen | <chemical> Hydrogen sulfide (h2s). A flammable, poisonous gas with a characteristic odour of rotten eggs. It is used in the manufacture of chemicals, in metallurgy, and as an analytical reagent. Chemical name: Hydrogen sulfide (H2S) (12 Dec 1998) |
| interspecies hydrogen transfer | <biology, ecology> The process in which organic matter is degraded anaerobically by the interaction of several groups of microorganisms in which hydrogen production and hydrogen consumption are closely coupled among species. (09 Oct 1997) |
| 3-chloro-D-alanine hydrogen chloride-lyase | <enzyme> Pseudomonas putida enzyme; forms cysteine from 3-chloro-d-alanine and hydrogen sulfide Registry number: EC 4.5.- Synonym: cahc-lyase, 3-chloro-d-alanine chloride-lyase (deaminating) (26 Jun 1999) |
| formate hydrogen lyase | <enzyme> Consists of EC 1.2.1.2, formate dehydrogenase, plus EC 1.12.1.2, hydrogen dehydrogenase Registry number: EC 1.- Synonym: formate dehydrogenase h, fdhh gene product, fdhf gene product, hyc gene product (26 Jun 1999) |
| acetosulfone sodium | 2-N-Acetylsulfamyl-4,4'-diaminodiphenylsulfone;a leprostatic administered orally. (05 Mar 2000) |
| acetrizoate sodium | Salt of 3-acetamido-2,4,6-triiobenzoic acid, a formerly used water-soluble radiographic contrast medium. (05 Mar 2000) |