Biological complexity:photosynthesis new research (Introduction)

by David Turell , Saturday, March 25, 2023, 18:32 (398 days ago) @ David Turell

New details of this very complex system:

https://phys.org/news/2023-03-high-precision-quantum-chemistry-super-efficient-energy.html

"Photosynthesis drives all life on Earth. Complex processes are required for the sunlight-powered conversion of carbon dioxide and water to energy-rich sugar and oxygen. These processes are driven by two protein complexes, photosystems I and II. In photosystem I, sunlight is used with an efficiency of almost 100%. Here a complex network of 288 chlorophylls plays the decisive role.

"A team led by LMU chemist Regina de Vivie-Riedle has now characterized these chlorophylls with the help of high-precision quantum chemical calculations—an important milestone toward a comprehensive understanding of energy transfer in this system. This discovery may help exploit its efficiency in artificial systems in the future.

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"The chlorophylls in photosystem I capture sunlight in an antenna complex and transfer the energy to a reaction center. There, the solar energy is used to trigger a redox process—that is to say, a chemical process whereby electrons are transferred. The quantum yield of photosystem I is almost 100%, meaning that almost every absorbed photon leads to a redox event in the reaction center.

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"The results of the study, which is featured on the cover of the journal Chemical Science, reveal so-called "red chlorophylls" that absorb light at slightly lower energies than their neighbors due to ambient electrostatic effects. As a result, their absorption spectrum is red-shifted. Analogously, the researchers also identified energy barriers between the antenna complex and the reaction center, among other places. "This seems surprising at first glance because there is no obvious gradient along which energy is transferred from the antenna complex to the reaction center," explains lead author Sebastian Reiter.

"Under physiological conditions, however, the entire photosystem I is subject to thermal fluctuations that overcome these energy barriers, as the relative energies of the chlorophylls change with respect to each other. In this way, new pathways into the reaction center can constantly open up, while others close. This, according to the core thesis of the authors, could be the key to the high efficiency of photosystem I."

Comment: without the great oxygenation event most forms of life would not exist. A natural event or a system guided by God? It looks designed to me.