Biochemical controls:photosynthesis roughly 100% efficient (Introduction)

by David Turell , Sunday, July 16, 2023, 00:58 (495 days ago) @ David Turell

At a quantum level from disordered biology:

https://bigthink.com/starts-with-a-bang/photosynthesis-100-efficient-quantum-physics/?u...

"In terms of energy, the “holy grail” of any physical system is 100% efficiency. It’s a near-impossible goal under most conditions, as from the moment any form of energy first gets transferred into a system, it inevitably gets lost to a variety of factors — heat, collisions, chemical reactions, etc. — before finally accomplishing the ultimate task it was designed for.

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"But nature has provided us with a very surprising exception to that rule: plants. The humble plant, along with other, more primitive photosynthetic organisms, absorbs a fraction of sunlight at specific (blue and red) wavelengths to convert that light (photon) energy into sugars via the complex process of photosynthesis. Yet somehow, despite obeying none of the above physical conditions, nearly 100% of that absorbed energy gets converted into electron energy, which then creates those sugars via photosynthesis. For as long as we’ve known about the underlying chemical pathway of photosynthesis, this has been an unsolved problem. But thanks to the interface of quantum physics, chemistry, and biology, we may finally have the answer, and biological disorder is the key.

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"The chlorophyll found in plants is only capable of absorbing and using sunlight over two particular narrow wavelength ranges: blue light that peaks at around 430 nanometers in wavelength and red light that peaks around 662 nanometers in wavelength. Chlorophyll a is the molecule that makes photosynthesis possible, and is found in all photosynthetic organisms: plants, algae, and cyanobacteria among them. (Chlorophyll b, another light-absorbing and photosynthesizing molecule found only in some photosynthetic organisms, has a different set of wavelength peaks.)

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"if we restrict ourselves to looking at only the individual photons that can excite the chlorophyll a molecule — photons at or near the two absorption peaks of chlorophyll a — the red-wavelength photons are around 80% efficient, while the blue-wavelength photons are over 95% efficient: close to that perfect, 100% efficiency after all.

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"The puzzle in all of this is why, for every photon that gets absorbed in that very first step, approximately 100% of those photons wind up producing excited electrons at the end of the last step? In terms of efficiency, there are really no known naturally occurring physical systems that behave in this manner. Yet somehow, photosynthesis does.

"Under most laboratory circumstances, if you want to make an energy transfer 100% efficient, you have to specially prepare a quantum system in a very particular way... And you need to impose as close to “lossless” conditions as possible, where no energy gets lost due to the internal vibrations or rotations of particles, such as propagating excitations known as phonons.

"But in the process of photosynthesis, absolutely zero of these conditions are present. The light that comes in is plain old white sunlight: composed of a wide variety of wavelengths, where no two photons have exactly the same energy and momentum. The absorptive system isn’t ordered in any way, as the distances between the various molecules isn’t fixed in a lattice but rather varies tremendously: on scales of several nanometers between even adjacent molecules. And these molecules are all free to both vibrate and rotate; there are no special conditions that prevent these motions from occurring.

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"It’s important to remember that, unlike in most physical laboratory systems, there isn’t an “organization” to the protein network in biological systems; they’re located and spaced irregularly from one another in what’s known as a heterogeneous fashion, where each protein-protein distance is different from the last.

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"A key finding of this research is that these light-harvesting proteins can only very efficiently transfer this energy over long distances because of the irregular and disordered spacing of proteins within the purple bacteria themselves. If the arrangement was regular, periodic, or organized in a conventional way, this long-distance, high-efficiency energy transport could not occur.

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"And this is what the researchers actually found in their studies. If the proteins were arranged in a periodic lattice structure, the energy transfer was less efficient than if the proteins were arranged in a “randomly organized” pattern, the latter of which is far more representative of how protein arrangements normally occur within living cells.

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"In other words, what we normally consider a “bug” of biology, that biological systems are inherently disordered by many metrics, may actually be the key to how photosynthesis occurs at all in nature.

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"We normally think of quantum physics as only being relevant for the simplest of systems. In truth, however, it’s the underlying explanation behind every non-gravitational phenomenon in our macroscopic world: from how particles bind together to form atoms to how atoms join to make molecules to the chemical reactions that occur between atoms and molecules to how photons are absorbed and emitted by those atoms and molecules."

Comment: an amazing deigned system, not by chance. Al the complex methodology omitted.