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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 .
[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]
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.
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 excites an electron in the pigment P680 at the core of photosystem II, which is transferred to the primary electron acceptor, pheophytin, leaving behind P680 +. The energy of P680 + is used in two steps to split a water molecule into 2H + + 1/2 O 2 + 2e - ( photolysis or light-splitting ).
The light produced is of lower intensity than the light produced by typical sonoluminescence and is not visible to the naked eye. The light and heat produced by the bubble may have no direct significance, as it is the shockwave produced by the rapidly collapsing bubble which these shrimp use to stun or kill prey.
The wavelengths produced by most photocytes fall close to 490 nm, although light as energetic as 250 nm is reportedly possible. [ 1 ] The variations of color seen in different photocytes are usually the result of color filters in other parts of the photophore that alter the wavelength of the light prior to exiting the endoderm .
Aequorea victoria, also sometimes called the crystal jelly, is a bioluminescent hydrozoan jellyfish, or hydromedusa, that is found off the west coast of North America.. The species is best known as the source of aequorin (a photoprotein), and green fluorescent protein (GFP); two proteins involved in bioluminescence.