User:Pheenee/sandbox

Metabolism
Photosynthesis takes place at reaction centers on the cell membrane, which is folded into the cell to form sacs, tubes, or sheets, increasing the available surface area.

Like most other photosynthetic bacteria, purple bacteria do not produce oxygen (anoxygenic), because the reducing agent (electron donor) involved in photosynthesis is not water. In some, called purple sulfur bacteria, it is either sulfide or elemental sulfur. The others, called purple non-sulfur bacteria (aka PNSB), typically use hydrogen although some may use other compounds in small amounts. At one point these were considered families, but RNA trees show the purple bacteria make up a variety of separate groups, each closer relatives of non-photosynthetic proteobacteria than one another.

The reaction centers create a charge separation through a series of favorable redox reactions, after the excitation of the special pigment pair P870. The reduction of quinones leads to the take up of 2 protons from the cytoplasm. When the quinones are eventually oxidized, they release the protons in the periplasmic side. This builds up a proton motive force that is used by ATP synthase to produce ATP from ADP and phosphate.The ATP is finally used in biosynthesis.

Metabolism
Purple bacteria are mainly photoautotrophic, but are also known to be chemoautotrophic and photoheterotrophic. They can be mixotrophs, capable of aerobic respiration and fermentation.

Like most other photosynthetic bacteria, purple bacteria are anoxygenic, and do not produce oxygen because the electron donor used is not water. In purple sulfur bacteria, the electron donors are mainly sulfide or elemental sulfur. Most purple non-sulfur bacteria (PNSB) are facultative anaerobes and are photosynthetic in the absence of oxygen, typically using hydrogen (although some may use metals and other organic compounds in small amounts). In aerobic conditions, PNSB can be chemotrophic.

Photosynthesis takes place at the intracytoplasmic photosynthetic membrane (ICM), where the photosynthetic pigments (i.e. bacteriochlorophyll, carotenoids) and pigment-binding proteins are invaginated into the cytoplasmic membrane, forming vesicular structures to increase surface area (i.e. chromatophore). Reaction centers (RC) on the ICM are surrounded by light-harvesting antenna complexes that absorb specific wavelengths of light and transfer excitation energy to the RC. The excited RC pigments P870 or P960 then transfer electrons in a cyclic manner, first reducing quinones QA and QB, then oxidizing them at the cytochrome bc1 complex. The electrons are then returned to the RC via cytochrome c2. The reduced quinone QB attracts two cytoplasmic protons and becomes QH2, eventually releasing them to be pumped into the periplasm by the cytochrome c1 complex. This builds up a proton motive force that is used by ATP synthase to produce ATP from ADP and phosphate.

Pheenee (talk) 06:33, 9 October 2017 (UTC)

Metabolism
Purple bacteria are mainly photoautotrophic, but are also known to be chemoautotrophic and photoheterotrophic. They can be mixotrophs, capable of aerobic respiration and fermentation.

Like most other photosynthetic bacteria, purple bacteria are anoxygenic, and do not produce oxygen because water is not the electron donor. In purple sulfur bacteria, the electron donors are mainly sulfide or elemental sulfur. Most purple non-sulfur bacteria (PNSB) are facultative anaerobes and are photosynthetic in the absence of oxygen, typically using hydrogen (although some may use metals and other organic compounds in small amounts). These electron donors provide the electrons needed for the reduction of NAD(P)+ to NAD(P)H in anabolism.

Photosynthesis takes place at the intracytoplasmic photosynthetic membrane (ICM), where the photosynthetic pigments (i.e. bacteriochlorophyll, carotenoids) and pigment-binding proteins are invaginated into the cytoplasmic membrane, forming vesicular structures to increase surface area. Reaction centers (RC) on the ICM are surrounded by light-harvesting antenna complexes that absorb specific wavelengths of light and transfer excitation energy to the RC. The excited RC pigments P870 or P960 then transfer electrons in a cyclic manner, first reducing quinones QA and QB, then oxidizing them at the cytochrome bc1 complex. The electrons are then returned to the RC via cytochrome c2. The reduced quinone QB attracts two cytoplasmic protons and becomes QH2, eventually releasing them to be pumped into the periplasm by the cytochrome bc1 complex. This builds up a proton motive force that is used by ATP synthase to produce ATP from ADP and phosphate. Alternatively, purple bacteria also utilize reverse electron flow to reduce NAD(P)+ to NAD(P)H since the excited RC does not have a high enough reduction potential for the rest of the ETC to reduce NAD(P)+.

Pheenee (talk) 06:23, 20 November 2017 (UTC) Note: Another user from the class with the same assigned article has chosen to edit the exact same section, so instead of just uploading what I have above I will add on the relevant/needed parts to their edited portion from mine. (Since their edit is well made and organized!)