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Quantum Mechanics Involved In Photosynthesis
Kristina at Science News writes "We all learn about photosynthesis in school: sunlight in, plant food out. Not well understood is how this process achieves its initial and uniquely high efficiency in capturing the energy of a photon. Quantum mechanics may be at work in the electron transfer process inside chloroplast, giving electrons the chance to consider many paths at once before choosing the best one."
We all learn about photosynthesis in school: sunlight in, plant food out.
Huh, apparently some of us learned about it differently than others. I seem to recall it having to do with water and carbon dioxide in and some extra oxygen left over?
Also, I think someone beat you to the punch back in 2007 when we covered this story the first time and we covered that part about the birds using quantum effects in 2008.
My work here is dung.
The process involves photons that are absorbed while exciting the energy of molecules OF COURSE quantum mechanics is involved. Coming up next, thermodynamics may be at work in volcanic eruptions.
Is there any way to incorporate string theory, membranes, dimensions, time travel, or wormholes into this explanation? Kaku has some speaking engagements and needs some buzz words along with the usual Star Trek references.
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Is it just me or is everything now being explained through Quantum Mechanics?
Don't understand why people make irrational decisions?
Quantum Mechanics may be at work.
Don't understand how photosynthesis happens?
Quantum Mechanics may be at work.
Don't understand contradictions in quantum mechanics?
Well, that is because sub-atomic paticles may have free will?
Can't we just credit God or something?
Quantum mechanics isn't some tool in nature's toolbox. QM is a way that humans describe all natural phenomena when we explain details of how it all works. QM is a universal framework for describing all the actions of everything that exists.
If scientists are coming up with a new QM description of a physical process like photosynthesis, it's not because they're just discovering that QM is involved. It's because they're figuring out how to describe the process in terms of QM.
In other news, physics turns out to be involved in how the brain works.
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make install -not war
We've been teaching that in physical biochemistry courses for decades. With examples. This is like saying "gravity may be at work in planetary orbits."
It is not new at all that quantum tunneling is an important mechanism in the electron transport chain. The iron-sulfur centers are optimally positioned to optimize the tunneling rate of electrons between them. They knew about this several years ago, when I learned this in an undergrad biophysics class.
Man: "Ah, but look at quantum photosynthesis. That something so incredibly convenient to life (plant and herbivore and omnivore animals) should arise by accident is inconceivable. It proves you exist, so therefore you don't."
God: "Oh dear, I hadn't... <logic>puff</logic>
In Liberty, Rene
Science has now discovered that one of the more universal concepts in physics applies to... just about everything above the subatomic scale!
News at 11.
Quantum mechanics has something to do with nuclear bombs, don't it? Shouldn't we be screaming in panic, that our plants might explode like a nuclear bomb at any second? You can't trust those plants, sitting creepy still all the time, plotting our nuclear destruction all the time. We should destroy them all, before they get us!
Oops, forgot to take the blue pill. Take the blue pill now, not the red one.
Who would win this election: Andrew Weiner vs Andrew Weiner's weiner.
This research has science a step closer to showing that the brain functions as a quantum computer. Having a quantum computer in our head would explain why we're not like classical computers and have "intelligence", "free will" and "awareness."
Scientists who dismiss quantum processes at work in the body due heat and other quantum noise have little imagination to realize how exquisitely nature works on the molecular level to solve problems like these.
Nearly everything involving chemistry is governed by quantum mechanics...
Actually all chemistry is governed by quantum mechanics. In fact practically everything we can explain is governed by quantum mechanics, the only exception being gravity and even then we think it is governed by QM we just have not found the right model. Of course for things that happen at human scale it is often easier to use a continuum-based approximation of QM...but it is still an approximation of the underlying QM.
QM is a universal framework for describing all the actions of everything that exists.
Except for gravity. We can quantize this but only if we put in an artificial energy cut off. Of course most of us physicists believe that there is a proper QM description of gravity to be found but we have not yet do so so we cannot yet say that it is described by QM.
Unless you doubt the validity of the field of quantum mechanics, then you probably have to acknowledge that it's "involved" in all physical phenomenon. I mean, when you ask for an explanation of a specific phenomenon, you might want to know more about the larger scale interactions and forces, but still, electrons are involved and they're doing stuff. Probably all sorts of quantumy stuff that would blow your mind.
However, it does seem like quantum mechanics would turn up as much more relevant when you're talking about the conversion of light into some kind of energy a living organism can use. When you get down to the level of trying to analyze what happens to an individual photon in the process, I don't know how anyone expected to avoid talking about quantum mechanics.
It's covered in physics, to the extent that photosynthesis and the photoelectric effect are used to demonstrate photons must have momentum. (The law of conservation of momentum requires that the momentum going in equals the momentum coming out, so if the electron has momentum, then the photon must also.)
It's a small world and it smells funny; I'd buy another if it wasn't for the money; Take back what I paid (SoM)
Eivind, who don't doubt that there's quantum effects going on in the brain, but see no need for them for explaining "intelligence" or "awareness", and know enough psychology to not see any need for "free will" to describe how the mind works.
Doubting the existence of evolution is like doubting the existence of China: It just shows that you're uninformed.
To be honest, the result here, while important, is entirely unsurprizing. What you're dealing with here is bound electrons, moving from say, a chlorophyll group to a tyrosine amino acid residue. There's nothing knew that electrons, in particular bound electrons (such as in an atom or molecule) can only be accurately described quantum-mechanically. Electrons move through QM 'tunneling' quite a bit, so you simply cannot accurately describe electron-transfer kinetics (which is what's going on here) without QM.
No, it does not. First off, it spells trouble that you seem to view that as a desired end result. Hardly a good way to do science. Second, there is no good reason to believe that the brain cannot be described in terms of straight-up chemistry and biochemistry. We don't know how the brain works, but that doesn't mean it's unexplainable in terms of what we already know. There are plenty of things we haven't fully understood in biochemistry, but that doesn't mean they're generally believed to be unexplainable in the current framework of things. Occam's razor would dictate that that idea should be disregarded until there is some evidence that would make it necessary. No such evidence exists.
Further, your 'philosophical' points are simply invalid. Quantum mechanics says nothing about 'free will', or philosophical determinism for that matter. Quantum mechanics can be interpreted in either way, and has; e.g. the Copenhagen interpretation is nondeterministic, whereas the Bohm interpretation is.
I work with applying quantum mechanics at the molecular level, in biochemical systems, all day long. I have yet to find anyone in my field who thinks there are macroscopic quantum-mechanical processes going on in the human body. That is not due to lack of imagination, it's due to experience with actual quantum mechanics. All chemistry is inherently quantum mechanical. Physics cannot explain an atom even, much less a molecule, with classical theory. The relationship between chemistry and biochemistry is well-understood. The quantum mechanics of chemistry is fairly well understood (due to people doing what I do). And transition in the chemical domain from what is quantum-mechanical to what is classically describable is also well understood. There is simply no physics that explains how or why quantum mechanical effects would disappear and then re-appear orders of magnitude 'upwards' on the scale of matter.
Quantum computers are Turing reducible. It doesn't matter if your computer is classical or quantum, they can still only solve the same kinds of problems. This goes for the brain as well. (For the philosophers, this means that we cannot so easily escape from Searle's Chinese room.)
All of this quantum mind nonsense seems to have stared with Roger Penrose and his ridiculous "theory". (Read: Shadows of the mind and The emperors new mind) He not only claims that the brain is a quantum system (possible, but totally unfounded) but also proposes a formula by which we can calculate how conscious something is! (He bites the ol' ontological bullet really hard, and goes on to claim that even an electron can be conscious, but only a little bit and only once in a great while.)
This article:
http://www.sciencemag.org/cgi/content/summary/287/5454/791?ck=nck
Very clearly outlines the biggest problems for the theory. This is likely where the "Brain is too hot" argument originated. It's a good one, and not likely to go away anytime soon.
More importantly, even if mother nature managed to work around the problem of a hot brain, it still doesn't get us any closer to consciousness. (See my first paragraph above) In the Penrose-Hameroff model, consciousness appears magically during collapse of the wave function. How they came to such a conclusion is beyond reason. That isn't science, it's mysticism.
Required reading for internet skeptics
I dunno. More people seem to be interested when the guy has a magician's hat than a scientist's lab coat.
It's a small world and it smells funny; I'd buy another if it wasn't for the money; Take back what I paid (SoM)
In other news, Kansas has passed legislation to allow the teaching of alternate theories of photosynthesis, including Intelligent DeShine. This theory argues that plants produce food from sunlight by the mediation of "christons", which have the mystical property of being three particles in one, allowing them to convert the sunny warmth of the 6000-year-old Sun into original sin-free gluten.
You didn't think the Eucharist was made out of wheat by accident, did you? Heathen.
"I guess the moral of the story is, don't paint your airship with rocket fuel." -- Addison Bain
I thought this was obvious after learning about photodiodes in electronics class.
It's not about the quantum nature of the absorption of the photon and its conversion to an excited electron state.
It's about the efficient propagation of that excited electron state, once created, from one molecule to another until it gets to a place where it can be used. "Picking the path" in a non-random way, without losing energy in the process, seems to be using quantum weirdness as well.
Bantam Dominique roosters crow a four-note song. Once you've heard it as "Happy BIRTHday" you can't NOT hear it that way
As a quantum physicist, perhaps I can enlighten those of you whose ignorant "of course it's quantum physics! clearly this research is the st00p1d" comments have gained unseemly amounts of modpoints.
Yes, of course quantum mechanics is what is ultimately responsible for everything that happens in the world (at least, as far as we know, though general relativistic phenomena are so far an exception to this). However, despite this fact, it is remarkably the case that the world we perceive on our own macroscopic level does not behave in a quantum way at all, but instead seems to obey classical mechanics. Essentially what it comes down to is that at some point, things start interacting with their environment so much that they start being constantly measured, and so the quantum behaviour disappears. What is not so clear is at exactly what level the world stops being quantum and starts being classical.
In general, the cutoff seems to be somewhere around a molecule. That is although atoms and bonds between atoms are quantum effects, molecules tend be very well modeled using classical forces that were obtained from the quantum models of the bonds.
Because of this, before this research was done, a very reasonable educated guess for one to have made was that the first step of photosynthesis, where an electron essentially is knocked into walking from one part of the molecule to another, would be a classical process, since it happens on the scale of a molecule. Put another way, one might have guessed that when the electron walked from one part of the molecule to another, it did so in a classical (but non-deterministic) fashion by choosing one of the paths available to it and walking down that.
However, what this research has shown is that this is not the case. The electron in fact takes several paths at once. This was detected by performing experiments which showed that there were interference effects; this is the standard approach to take to determine whether something is quantum or classical by the following rough chain of reasoning: you can only see interference patterns when you have cancellations, and you can only see cancellations when something has taken two paths simultaneously but with the opposite phase, so ergo if you see an interference pattern then something quantum must be going on.
This is actually very remarkable because it means that nature specifically engineered a molecule that manifests quantum behaviour on a larger scale then it usually appears. This is a non-trivial thing to have done because, again, the fact that we don't usually see quantum behaviour on this scale implies that it is typically precluded by interactions with the environment, so the fact that this molecule accomplishes this means that it somehow evolved to isolate the electrons involved in photosynthesis from their environment in order to allow them to act in a quantum fashion.
It turns out that the gain from doing this is small, but notable; I didn't read the article, but I did talk to some of the people involved in this research at a couple of meetings and if recall correctly they said that according to their simulations, by doing this nature gained an efficiency of about 10% over what it would be able to get if it were only using classical phenomena. Thus, this effect is actually important for us to understand because it may give us insights into how we can engineer our own devices to use large-scale quantum phenomena to more efficiently harness energy from the sun.
Snarkiness is inversely proportional to wisdom because it emphasizes feeling right rather than being right.
Nothing science has put forth even attempts to explain why I have a sense of me.
People put way too much importance on that. Your brain is telling you that you have a sense of yourself. Take some of the right drugs and suddenly you can have your brain giving you a sense that you're everyone and everything else too. Doesn't make it true.
It's possible, and in fact likely, that what you perceive as free will and consciousness is an illusion of very complex, but completely deterministic behavior. You haven't offered anything to explain why that wouldn't be the case.
If we manage to figure that one out, the next step would be to explain why anything exists at all.
The question of "why does anything exist at all" is utterly meaningless. If nothing existed at all, the mystery would be "why is there only nothingness?" except there would be nobody to ask the question. The mysteries are still equivalent.
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Most of the time it can be disregarded. Now is an appropriate time for a car analogy and discussion about how quantum effects can be ignored when designing a timing belt.
Fascism trolls keeping me up every night. When I starts a preachin', he HITS ME WITH HIS REICH!