Slashdot Mirror
Photosynthesis May Rely On Quantum Effect
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."
I wonder if ferns ever look at us and laugh saying that non-quantum-sourced energy is so 3 billion years ago.
I'm sorry, please clarify: did you actually say anthing in that post?
... it's also been discovered that *all* physical phenomena may also rely on Quantum Effect.
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.
Was there any specific quantum effect you had in mind or did your spell checker mysteriously substitute the phrase "quantum effects" for the word magic ?
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.
Real Daleks don't climb stairs - they level the building.
It was actually featured in a Slashdot story not long ago:
1 1/1952201
0 4-10.html). The guy behind the work is one Dr. Lucia Turin, and he has indeed achieved some commercial success through his company Flexitral.
http://science.slashdot.org/article.pl?sid=06/12/
Unfortunately, the original Nature article is now subscriber only (http://www.nature.com/news/2006/061204/full/0612
When a photon strikes a chlorophyll, it adds its energy to an electron, allowing the electron to escape from its atom (previously known quantum mechanics). It was previously thought that the electron would then go bouncing around between chlorophyll molecules until it found a pheophytin molecule (slightly different chlorophyll). Once it hits that molecule, it activates an electron-transport chain (a similar process happens when burning glucose in a mitochondrion).
TFA suggests that the hopping uses quantum superposition to traverse the chlorophyll molecules more quickly. When the traversal reaches the pheophytin, the superposition collapses into that single state which found the pheophytin.
(IANAL)
The summary is slightly misleading, but this disconnect has big implications for the reader's understanding (imho)...
j ablonski.gif Unfortunately, this scheme doesn't show photofragmentation or energy transfer to another molecule, but I'm in a rush so it'll do.
I can name plenty of chemical reactions that are complete on the femtosecond scale, and while speed helps, that's certainly not the whole picture. What matters is how mismatched the energy levels between the reactant and the product are. When transitioning between energy levels, either energy is transferred out of the system by nonradiative release (heat), luminescence, photofragmentation, or transfer to a chemical partner - this last case is what the article is referring to. Getting to an energy level which can react is going to result in a heat deposition for at least some photons because any photon of a higher energy than the reacting state must deposit some of that energy just to be able to react at all.
http://www.monos.leidenuniv.nl/smo/basics/images/
The squiggly lines show possible heat depositions - the molecule starts in the ground state, absorbs a photon (the yellow up arrow), then relaxes to the excited state. This excited state then does whatever it's going to do. If 100% of the time under a set of conditions (i.e. a quantum yield of 1.00), the excited molecule follows a particular pathway we call that perfectly efficient. In the specific example of photosynthesis, this means that all of the absorbing chlorophylls transfer the energy along the photosynthetic pathway (I'm lumping all the subsequent processes together here). It does not mean that 100% of the energy got transferred along the way - there will always be some photon that deposits more energy than the reacting state has, meaning some energy will be converted to heat.
In short form (if you didn't feel like reading all this): efficiency in this case refers primarily to how often the molecule dumps its energy into photosynthesis instead of all to heat, luminescence, etc. It's not referring to the energy throughput, as some photons will always be an imperfect energy match, and the extra energy will end up as heat.
Be careful of your thoughts; they could become words at any minute...
Yeah, sure the energy transfer efficiency is 100% for every photon that participates in the reaction. But of all the photons falling on the leaf, hardly 2% of them participate in reactions. Some gets reflected, some gets absorbed without any reaction. Even solar cells have better energy conversion efficiency than plants. Really. As for quantum effects, almost all the photo reactions are quantum mechanics. They have to be. The film camera emulsion has greater percentage of photons participating in reaction than chlorophyll.
sed -e 's/Chuck Norris/Rajnikant/g' joke > fact
I believe he said, "I'm high."
W..w..W - Willy Waterloo washes Warren Wiggins who is washing Waldo Woo.