====== Photosynthesis ======

>Photosynthetic water splitting (or oxygen evolution) is one of the most important reactions on the planet, since it is the source of nearly all the atmosphere's oxygen [...]__ The mechanism of water oxidation is still not fully elucidated,__ but we know many details about this process." \\ \\ Source : [[https://en.wikipedia.org/wiki/Photosystem_II|Wikipedia]]

After many decades of research, much of the fine-detail of the highly complex photosynthesis (PS) process is now understood. It's now known, for example, that four photons are required to initiate PS, and that it takes only a millisecond or so to split water to produce oxygen as a by-product. (For complex technical details, see the two //Nature// papers linked below.)

Several crucial steps, however, remain undescribed.

Current research suggests that the oxygen moves through stages which include a complex peroxide - but the exact details are still not known :

>The onset of O<sub>2</sub> evolution, as indicated by the shortening of the Mn1–Mn4 distance, occurs at around 1,200 μs, signifying the presence of a reduced intermediate, possibly a bound peroxide."\\ \\ Source : [[https://www.nature.com/articles/s41586-023-06038-z.pdf|Structural evidence for intermediates during O2 formation in photosystem II]]{{:oa_padlock_grn.png?16}}//Nature,// May 2023

For further extensive technical details see :  [[https://www.nature.com/articles/s41586-023-06008-5.pdf|The electron–proton bottleneck of photosynthetic oxygen evolution]]{{:oa_padlock_grn.png?16}}//Nature,// May 2023

=== PS efficiency ===

The efficiency of photosynthesis (PS) is thought to be very close to 100% (exceptionally high for any complex system) which has led some researchers to suggest that quantum [[https://en.wikipedia.org/wiki/Quantum_superposition|'superposition']] effects and/or [[content:physics:quantum_physics:entanglement|quantum entanglement]] may be in operation with respect to the way that photons are somehow channeled towards the most efficient pathways within the light-harvesting complexes. These theories have not yet been generally accepted.

Example research paper :

>Photosynthetic  organisms  capture  visible  light  in  their  light-harvesting  complex  and transfer the excitation energy to the reaction center which stores the energy from the photon in chemical bonds.  This process occurs with nearly perfect efficiency." [...] __"The high efficiency of this process is not yet understood today."  __\\ \\ Source : __ BROKEN-LINK:[[https://arxiv.org/pdf/1702.08257.pdf|Gain and loss in open quantum systems]]LINK-BROKEN__, Institute for Quantum Science and Engineering, Texas A&M University, and Max Planck Institute for the Physics of Complex Systems, 2017

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Also see [[content:life_sciences:botany:oxygen_process]] and [[content:life_sciences:botany:rubisco_anomaly]]

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