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."

Comments

Re:Quantum Mechanics

[Anonymous Coward]

Quantum Mechanics IS God!

Dun, dun, dunnnnn!

Newsflash....

[tnk1]

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.

Except gravity

[Roger W Moore]

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.

Re:Except gravity

[Doc Ruby]

Sure, but QM is still a framework for describing everything that exists. That doesn't mean it's a complete framework, even though it's largely complete, and more complete all the time.

Photosynthesis is fully described by QED. That doesn't mean that photosynthesis "uses QM", any more than it "used phlogistons" if it were described analytically in the early 1800s. Or rather, photosynthesis "uses" QM, or phlogistics, or whatever other framework is being used to describe photosynthesis more or less accurately.

The point is that QM is not a process, like "electron cascade", that photosynthesis "uses". It's a framework within which to describe processes like electron cascades that photosynthesis uses.

If we were describing photosynthesis solely in terms of gravitational phenomena, then it might be remarkable to say that our explanation uses QM to describe what happens, because QM doesn't accurately describe gravitation. But that's not what we've got in this case.

Besides, the QM of photosynthesis has been described for quite a while. A new wrinkle in it does not merit a headline announcing that QM is involved.

Photoelectric Effect

[jd]

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.)

Re:"Quantum mechanics may be at work"

[Zatacka]

There is no reason to believe NP-complete problems can be solved in polynomial time (let alone constant time) on a quantum computer.

Re:A step closer to the brain as a quantum compute

[narcc]

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.

Re:A step closer to the brain as a quantum compute

[TrekkieGod]

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.

Re:Of Course It "Uses Quantum Mechanics"

[mdielmann]

The difference is, some things can be adequately described without QM. What they're saying is, photosynthesis can't. I can explain plenty of things in Newtonian physics, some more in General Relativity.
It's kind of like when they discovered how flies fly a few years back. Sure, we knew they could fly, we even knew a great deal about the mechanics involved. But to really figure it out, they had to do some serious testing. What they learned is that flies use 3 different techniques to generate lift, in every flap of their wings. That's what was new in that particular study.
Greater understanding comes one step at a time. Given what we know now, perhaps we can build better devices to harness light energy. Or perhaps it will take us in a brand new direction. We'll see.