| photosynthesis | <biochemistry, biology> Process by which green plants, algae and some bacteria absorb light energy and use it to synthesise organic compounds (initially carbohydrates). In green plants, occurs in chloroplasts, that contain the photosynthetic pigments. Occurs by slightly different processes in C3 and C4 plants. (18 Nov 1997) |
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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) |
| 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) |
| photosystem | <plant biology> The functional set of light-absorbing pigments (chlorophyll, etc.) and a reaction centre in photosynthetic organisms. (09 Oct 1997) |
| photosystem I | <plant biology> Photosynthetic system in chloroplasts in which light of up to 700 nm is absorbed and its energy used to bring about charge separation in the thylakoid membrane. The electrons are passed to ferredoxin and then used to reduce NADP to NADPH noncyclic electron flow or to provide energy for the phosphorylation of ADP to ATP (cyclic photophosphorylation). (18 Nov 1997) |
| photosystem II | <plant biology> Photosynthetic system in chloroplasts in which light of up to 680 nm is absorbed and its energy used to split water molecules, giving rise to a high energy reductant, Q and oxygen. The reductant is the starting point for an electron transport chain that leads to photosystem I and that is coupled to the phosphorylation of ADP to ATP. (18 Nov 1997) |
| photosystem II D1 polypeptide carboxy-terminal processing protease | <enzyme> From thylakoids; not inhibited by common protease inhibitors Registry number: EC 3.4.99.- Synonym: d1 carboxy-terminal processing protease, d1 c-terminal protease, ctpa gene product (26 Jun 1999) |
| phototaxis | <cell biology> Movement of a cell or organism towards (positive phototaxis) or away from a source of light (negative phototaxis). (18 Nov 1997) |
| phototherapy | Treatment with light. For example, a newborn with jaundice may be put under the lights. (12 Dec 1998) |
| photothermal | Relating to radiant heat. Origin: photo-+ G. Therme, heat (05 Mar 2000) |
| phototimer | An electronic device in radiography that measures the radiation that has passed through the patient and terminates the X-ray exposure when it is sufficient to form an image. (05 Mar 2000) |
| phototonus | <botany> A motile condition in plants resulting from exposure to light. Phototon"ic. Origin: NL. See Photo-, and Tone. Source: Websters Dictionary (01 Mar 1998) |
| phototoxic | Relating to, characterised by, or causing phototoxis. (05 Mar 2000) |