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Photosystem II (or water-plastoquinone oxidoreductase) is the first protein complex in the light-dependent reactions of oxygenic photosynthesis. It is located in the thylakoid membrane of plants , algae , and cyanobacteria .
They are non-thermal in origin, and the emission of biophotons is technically a type of bioluminescence, though the term "bioluminescence" is generally reserved for higher luminance systems (typically with emitted light visible to the naked eye, using biochemical means such as luciferin/luciferase).
The light-harvesting system of PSI uses multiple copies of the same transmembrane proteins used by PSII. The energy of absorbed light (in the form of delocalized, high-energy electrons) is funneled into the reaction center, where it excites special chlorophyll molecules (P700, with maximum light absorption at 700 nm) to a higher energy level.
[citation needed] He called them cancroïde, later changing the name to chéloïde to avoid confusion with cancer. The word is derived from the Ancient Greek χηλή, chele, meaning "crab pincers", and the suffix -oid, meaning "like". In the 19th century it was known as the "Keloid of Alibert" as opposed to "Addison’s keloid" . [24]
In some animals, the light is bacteriogenic, produced by symbiotic bacteria such as those from the genus Vibrio; [2] in others, it is autogenic, produced by the animals themselves. In most cases, the principal chemical reaction in bioluminescence involves the reaction of a substrate called luciferin and an enzyme , called luciferase .
The bioluminescence can be produced from compounds during the digestion of prey, from specialized mitochondrial cells in the organism called photocytes ("light producing" cells), or, similarly, associated with symbiotic bacteria in the organism that are cultured.
Imaging of engineered E. coli Nissle 1917 in the mouse gut. Bioluminescence imaging (BLI) is a technology developed over the past decades (1990's and onward). [1] [2] [3] [when?] that allows for the noninvasive study of ongoing biological processes [4] [1] [5] [6] [7] Recently, bioluminescence tomography (BLT) has become possible and several systems have become commercially available.
The only light source in the deep sea, marine animals give off visible light energy called bioluminescence, [23] a subset of chemiluminescence. This is the chemical reaction in which chemical energy is converted to light energy. It is estimated that 90% of deep-sea animals produce some sort of bioluminescence.