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The Purple Earth Hypothesis (PEH) is an astrobiological hypothesis, first proposed by molecular biologist Shiladitya DasSarma in 2007, that the earliest photosynthetic life forms of Early Earth were based on the simpler molecule retinal rather than the more complex porphyrin-based chlorophyll, making the surface biosphere appear purplish rather ...
Cornelis Van Niel made key discoveries explaining the chemistry of photosynthesis. By studying purple sulfur bacteria and green bacteria, he was the first to demonstrate that photosynthesis is a light-dependent redox reaction in which hydrogen reduces (donates its atoms as electrons and protons to) carbon dioxide.
Two classes of reaction centres are recognized. Type I, found in green-sulfur bacteria, Heliobacteria, and plant/cyanobacterial PS-I, use iron sulfur clusters as electron acceptors. Type II, found in chloroflexus, purple bacteria, and plant/cyanobacterial PS-II, use quinones.
Purple bacteria use bacteriochlorophyll and carotenoids to obtain the light energy for photosynthesis. Electron transfer and photosynthetic reactions occur at the cell membrane in the photosynthetic unit which is composed by the light-harvesting complexes LHI and LHII and the photosynthetic reaction centre where the charge separation reaction ...
Purple nonsulfur bacteria used a variety of nonspecific organic and inorganic molecules. It is suggested that photosynthesis likely originated at low-wavelength geothermal light from acidic hydrothermal vents, Zn-tetrapyrroles were the first photochemically active pigments, the photosynthetic organisms were anaerobic and relied on H 2 S without ...
Neutrophil - Wikipediawikipedia.org- Play Poker Texas Holdem Online for Freeaol.com
Photosystems are functional and structural units of protein complexes involved in photosynthesis. Together they carry out the primary photochemistry of photosynthesis: the absorption of light and the transfer of energy and electrons. Photosystems are found in the thylakoid membranes of plants, algae, and cyanobacteria.
Anoxygenic photosynthesis is a special form of photosynthesis used by some bacteria and archaea, which differs from the better known oxygenic photosynthesis in plants in the reductant used (e.g. hydrogen sulfide instead of water) and the byproduct generated (e.g. elemental sulfur instead of molecular oxygen ).
In general, photosynthesis in cyanobacteria uses water as an electron donor and produces oxygen as a byproduct, though some may also use hydrogen sulfide a process which occurs among other photosynthetic bacteria such as the purple sulfur bacteria. Carbon dioxide is reduced to form carbohydrates via the Calvin cycle.
Photosynthesis (1931) By studying purple sulphur bacteria and green sulphur bacteria he was the first scientist to demonstrate, in 1931, that photosynthesis is a light-dependent redox reaction in which hydrogen from an oxidizable compound reduces carbon dioxide to cellular materials. Expressed as: 2 H 2 A + CO 2 → 2A + CH 2 O + H 2 O
The antenna complex in purple photosynthetic bacteria are protein complexes responsible for the transfer of solar energy to the photosynthetic reaction centre. Purple bacteria, particularly Rhodopseudomonas acidophila of purple non-sulfur bacteria, have been one of the main groups of organisms used to study bacterial antenna complexes so much ...