Want to read Slashdot from your mobile device? Point it at m.slashdot.org and keep reading!

 



Forgot your password?
typodupeerror
Biotech Science

Photosynthesis May Rely On Quantum Effect 234

Posted by kdawson
from the good-exitations dept.
forgethistory sends us to PhysOrg for a summary of new research suggesting that the near instantaneous energy transfer achieved by photosynthesis may rely on quantum effects. From the article: "Through photosynthesis, green plants and cyanobacteria are able to transfer sunlight energy to molecular reaction centers for conversion into chemical energy with nearly 100-percent efficiency. Speed is the key — the transfer of the solar energy takes place almost instantaneously so little energy is wasted as heat. How photosynthesis achieves this near instantaneous energy transfer is a long-standing mystery that may have finally been solved."
This discussion has been archived. No new comments can be posted.

Photosynthesis May Rely On Quantum Effect

Comments Filter:
  • I don't know about consciousness, but in his novel Blue Mars [amazon.com] (last book of the Mars trilogy), published a decade ago already, Kim Stanley Robinson made use of research that suggests that memory relies on a quantum effect.
  • by Zeinfeld (263942) on Friday April 13, 2007 @08:56AM (#18717699) Homepage
    Knowing a possible mechanism is important, yes, but that's a long way from having a workable implementation of the method that is useful in a technological sense.

    All interactions at the atomic level are quantum effects. A photon can only interact through quantum effects. The statement in the article is totally meaningless.

    We have known that photosynthesis is a quantum effect since Einstein's paper on black body radiation.

  • by RobertB-DC (622190) * on Friday April 13, 2007 @08:57AM (#18717711) Homepage Journal
    I can't seem to find the link (Google is not friendly today), but does this perhaps justify the researcher who postulated that the sense of smell comes from something akin to detecting nuclear resonance, not a simple chemical interaction? I recall that one detractor said that his theory was as outlandish as saying that food was digested in the stomach via tiny nuclear reactors. But it explained many things that didn't make sense otherwise -- like why cyanide smells like almonds.

    He's apparently gone on to success in the perfume industry.

    Someone find the link... this is driving me nuts.
  • by meringuoid (568297) on Friday April 13, 2007 @08:59AM (#18717731)
    I don't know about consciousness, but in his novel Blue Mars (last book of the Mars trilogy), published a decade ago already, Kim Stanley Robinson made use of research that suggests that memory relies on a quantum effect.

    Would that mean that attempts to upload human minds to computers would fall foul of the no-cloning theorem? Such constraints on the duplication of quantum information would have interesting effects on philosophical problems of identity.

  • by spottedkangaroo (451692) * on Friday April 13, 2007 @09:05AM (#18717797) Homepage
    In one of the various debunkings of What the *bleep* do we know they cover that the neuronal activity in your brain is way too big to be affected by the very small quantum strangenesses that come up. On average they have no effect on your thinking.
  • by mattpalmer1086 (707360) on Friday April 13, 2007 @09:16AM (#18717933)
    Why do you need to invoke one mystery to "explain" another? I can't see why consciousness "may not be so easily explained without taking into account quantum effects". What particular things about consciousness seem to indicate quantum effects to you?

    Other people have proposed this before, but present a theory of why quantum effects may be necessary. Roger Penrose makes the argument that we can compute things that a Turing-style computer could not compute, so something else must be going on. His proof that some things we do cannot be done by a Turing style computer isn't exactly accepted though, and no-one seriously believes that the brain works in this way in any case.

    Also, consciousness is not the same thing as "self-awareness". Is a dog conscious? Is it self-aware? What about a rabbit? When I dream, I'm not usually self-aware, but there's some sort of consciousness there. What about phenomena like blind-sight, where a person is self-aware, but unconscious of visual information, even though they can access that information by guessing remarkably accurately, just without any direct consciousness of it. Does this mean that these supposed quantum-consciousness effects have broken down only for information originating in visual centers, but keeps working on all other information?

    Of course, coming from quantum theory, there is the Copenhagen Interpretation which places a special status on the 'observer' - but no-one has managed to define what an observer is, or whether they must be conscious or not.

  • by JDevers (83155) on Friday April 13, 2007 @09:19AM (#18717983)
    Maybe a better summary would be that the energy transfer in photosynthesis is handled by a very long lived wavelike electronic quantum coherence. Regardless of what everyone on /. thinks, this is a pretty big deal. Suggesting something is likely or even almost certain is not the same thing as proving it.
  • by DrWho520 (655973) on Friday April 13, 2007 @09:20AM (#18718015) Journal
    Yes, but while knowing the mechanism netted someone their PhD (or some PhD their tenure,) a workable implementation will net some company billions of dollars. Nearly 100% efficient solar cells? Yes, please. Pass the chlorophyll over here.
  • by denoir (960304) on Friday April 13, 2007 @10:13AM (#18718739)

    There are probably a lot of functions like photosynthesis that rely on quantum effects. One of them might be the idea of consciousness. Consciousness may not be so easily explained without taking into account quantum effects. If self awareness is enabled through some sort of quantum effect, imagine the philosophical implications.
    It's called the Orch-OR theory [wikipedia.org] and is a popular object of ridicule amongst neuroscientists. While consciousness is a very active field of research and there is still much to be done, it is very clear that the brain does not work at the quantum level. Being a warm moist place, it is actually one of the worst possible locations for quantum coherence.

    Contrary to popular belief, consciousness is not all that mysterious. We can with our knowledge today say with pretty good certainty that it's a post processing effect. After other mechanisms in the brain have done their processing and made a decision, consciousness kicks in in order to map the responses of the various parts of the brain into a coherent symbolic higher-level structure. Basically consciousness tries to explain on what grounds a decision is made in order to facilitate deductive reasoning.

    The funny thing is that there is a quite long delay (average 500 ms) between when a decision is made in parts of the brain that you are not aware of to when you are aware of decision - and think that your consciousness is involved in making that decision. In reality the decision has been made a long time ago without the consciousness being involved.

    The Orch-OR theory and similar ones are mainly a desperate attempt to explain away the data that rules out conscious thought as a first cause of decision. In reality though, consciousness is just another example of human exceptionalism that we have to abandon - just like we had to learn to live with the fact that earth is not at the center of the universe.

  • Re:100% efficiency (Score:5, Interesting)

    by 140Mandak262Jamuna (970587) on Friday April 13, 2007 @10:43AM (#18719177) Journal
    I am not arguing that the research is worthless or that it might some day create Organic photocell. Infact I tried to make a joke about Organic Light Absorbing diodes yesterday in the LED thread and mangled it and got modded down as troll. It would be great if we could unlock the secret of photosynthesis and understand why its efficiency is so low ( less than 2%) so that we can develop more efficient organic cells. My only complaint was that, the summary is very misleading, talking about 100% efficiency.

    But one thing we should also realize is that, nature has not produced a more efficient photosyntesis process. Plants do not use their energy for mobility. Just to grow. Growth is limited by other resources like minerals and water. So there might not be additional survival value in developing a more efficient photosynthesis process. But still we should be open to the possibility that 2% efficiency is probably the maximum for photosynthesis, using water+co2, producing C12H22O11 (sugar) and oxygen.

  • by Rei (128717) on Friday April 13, 2007 @10:59AM (#18719427) Homepage
    Well, that's only part of the story. The original capture loses very little energy...

    1) If and only if the photon is of the proper energy. In general, during solar energy conversion of all kinds, you require a certain amount of energy to kick an electron out of the pigment. Less than that energy, and nothing happens. More than that energy, and the excess is wasted.

    2) This only applies to the original photon capture. The total process of turning solar energy to sugars in plants is about 35%. Due to losses for biochemistry, the overall system is very inefficient -- usually just 1-2% in most crop plants, and a fraction of a percent in non-crop plants. Sugarcane is exceptionally high at 8%, still well below most silicon cells.

    Now, dye-based cells *are* in development. The key for them is not that they're very efficient (they tend to be very inefficient), but that they should be very cheap to produce (no silicon refining needed). Of course, a few companies (such as Nanosolar [nanosolar.com]) are working on commercializing high-efficiency dye-based cells. I read nanosolar's main patent at one point; basically, the efficiency problem with most organic solar cells is an uneven distribution of electron donors and receivers that leads to most of the electrons being wasted. In Nanosolar's case, they build a crystalline scaffolding that the dye gets embedded into at regular intervals, then dissolve the scaffolding.
  • by jakosc (649857) * on Friday April 13, 2007 @11:02AM (#18719463) Homepage
    To clarify, it's not the electron itself that traverses the chlorophyll molecule(s), but the energy of the electron (somewhat analogous to kinetic energy transfer in Newton's Cradle [wikipedia.org]). See also (Resonance Energy Transfer [wiley.com])
  • [ignore this] (Score:1, Interesting)

    by Anonymous Coward on Friday April 13, 2007 @11:13AM (#18719615)
    Undoing bad mod.

Riches: A gift from Heaven signifying, "This is my beloved son, in whom I am well pleased." -- John D. Rockefeller, (slander by Ambrose Bierce)

Working...