| photosynthetic unit | <biochemistry, plant biology> Group of photosynthetic pigment molecules (chlorophylls and carotenoids) that supply light to one reaction centre in photosystem I or II. (18 Nov 1997) |
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| gram-negative oxygenic photosynthetic bacteria | <microbiology> Widely distributed unicellular or multicellular bacteria. The cyanobacteria use chlorophyll a and phycobilins for oxygenic photosynthesis while genera in the prochlorales use both chlorophyll a and b but not phycobilins. (12 Dec 1998) |
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| photosynthetic bacteria | <microbiology> Bacteria that are able to carry out photosynthesis. Light is absorbed by bacteriochlorophyll and carotenoids. Two principal classes are the green bacteria and the purple bacteria. (31 Dec 1997) |
| photosynthetic reaction centre, bacterial | A system consisting of proteins and cofactors which acts as a light-driven electron pump across the photosynthetic membrane of photosynthetic bacteria. (12 Dec 1998) |
| photosynthetic reaction centre, plant | A system consisting of proteins and cofactors which facilitates light energy and electron transfer in plants. (12 Dec 1998) |
| absolute unit | A unit whose value is constant regardless of place or time and not derived from dependent on gravitation. (05 Mar 2000) |
| alexin unit | The smallest amount (highest dilution) of complement that will cause haemolysis of a unit of red blood cells in the presence of a haemolysin unit. Synonym: alexin unit. (05 Mar 2000) |
| Allen-Doisy unit | The quantity of oestrogen capable of producing in a spayed mouse a characteristic change in the vaginal epithelium, namely, disappearance of leukocytes and appearance of cornified cells, as determined by a vaginal smear; equal approximately to one-half of an estrone unit. Synonym: mouse unit. (05 Mar 2000) |
| amboceptor unit | haemolysin unit |
| androgen unit | The androgenic activity of 100 ug (0.1 mg) of crystalline androsterone as assayed by the comb growth response in capons. (05 Mar 2000) |
| antigen unit | The smallest amount of antigen that, in the presence of specific antiserum, will fix 1 complement unit. (05 Mar 2000) |
| antitoxin unit | A unit expressing the strength or activity of an antitoxin; in general, determined with reference to a preserved standard preparation of antitoxin. See: L doses. (05 Mar 2000) |
| antivenene unit | The amount of antivenum which, injected in the ear vein, will protect 1 g weight of rabbit against a fatal dose of snake venom. (05 Mar 2000) |
| atomic mass unit | <chemistry> One-twelfth the mass of a neutral atom of the most abundant isotope of carbon. (16 Dec 1997) |
| Bethesda unit | A measure of inhibitor activity: the amount of inhibitor that will inactivate 50% or 0.5 unit of a coagulation factor during the incubation period. Origin: Bethesda, MD (05 Mar 2000) |
| biological standard unit | A specific quantity of biologically active reference material (antibiotic, antitoxin, enzyme, hormone, vitamin, etc.). (05 Mar 2000) |