Advertisement
RayBiotech
RayBiotech

Quantum photosynthesis

Biologists have traditionally left quantum theory to physicists. But the complicated interactions between matter and energy predicted by quantum mechanics appears to play a role in photosynthesis, according to a study published this week in Nature -- affecting how energy from the sun makes its way to a cell's reaction centers before being converted to chemical energy that powers cellular functions. Cryptophye algae from the ocean(species Rhodomonas)Image: Dr. Tihana Mirkovic,University of Toron

By | February 3, 2010

Biologists have traditionally left quantum theory to physicists. But the complicated interactions between matter and energy predicted by quantum mechanics appears to play a role in photosynthesis, according to a study published this week in Nature -- affecting how energy from the sun makes its way to a cell's reaction centers before being converted to chemical energy that powers cellular functions.
Cryptophye algae from the ocean
(species Rhodomonas)

Image: Dr. Tihana Mirkovic,
University of Toronto
"The main surprise was that you could actually see" these quantum effects influencing real world biology, said biophysicist linkurl:Rienk van Grondelle;http://www.nat.vu.nl/%7Erienk/ of VU University in Amsterdam, who did not participate in the work, and "that you could observe this phenomenon underlying how [photosynthesis] was working." Quantum mechanics is a theory that describes the behavior of subatomic particles such as photons and electrons. But scientists have long believed that predictions made by the theory would only be evident in an idealized world that lacks environmental noise of molecules moving around and bumping into one another. People thought that "at room temperature, the noisy environment would kill this kind of quantum interaction," said van Grondelle, who wrote an accompanying review in Nature. But examining the light-harvesting systems of two species of photosynthetic algae, physical chemist linkurl:Gregory Scholes;http://www.chem.utoronto.ca/staff/SCHOLES/scholes_home.html of the University of Toronto and his colleagues observed that energy introduced to the system acted in a distinctly quantum manner, even at ambient temperatures. In these algae, bilin pigments, like other light-harvesting antenna molecules, absorb solar photons, which excite their electrons. The resulting excitation energy then moves to complexes of proteins called reaction centers, where it is converted to chemical energy by a series of biochemical events. While classical energy transfer theory predicts that the energy "hops, hops, hops" from one molecule to the next in a kind of "random walk," Scholes explained, quantum theory predicts that energy flows through the system in a much more spread-out, directed fashion. "Think about it as the energy moving [through the system] like a wave rather than like a ball bouncing from one molecule to another," said physical chemist linkurl:Graham Fleming;http://www.cchem.berkeley.edu/grfgrp/ of the University of California, Berkeley, who was not involved in the research. Instead of traveling a single pathway -- one molecule to the next -- the wave-like energy can actually take three different pathways simultaneously, Scholes said. This wave-like motion provides the energy with a "memory" of where it's been that eliminates some of the randomness of how it moves through the cell, explained van Grondelle. "[It] can still follow many paths," he said, "[but] it will be certainly more directed" than the random walk of classic energy transfer. To examine whether quantum effects played a role in photosynthetic algae, the researchers excited the electrons in a pair of bilin molecules with two short laser pulses, mimicking the natural process normally initiated by the sun, albeit at a much higher intensity. Adding a third pulse just a fraction of a second after setting the energy flow in motion elicited a "photon echo" -- a beam of light emitted from the system that served as a snapshot of how the energy was distributed at that particular moment. Piecing together these snapshots, the researchers could see how the energy moved over time, and identified distinct oscillations in the echo, indicating that the principles of quantum mechanics were at play. "The fact that [the photon echo had] weaker and stronger parts to it periodically is a signature of the quantum effects," Fleming said. Otherwise, "it would just go down smoothly until it was zero." Similar quantum effects have also been documented in a widely-studied light-harvesting organism, purple bacteria; this new study, though, is the first to document these effects in the normal function of photosynthetic eukaryotes that convert carbon dioxide to oxygen. Exactly how these quantum interactions affect the process of photosynthesis remains to be seen, said Scholes. The fact that energy movement may not be completely random "doesn't necessarily mean the system is more efficient," he said. "It's more subtle than that." In fact, if different waves interfered with one another in a certain way, it "could [actually] make the system less efficient," he noted. But in some cases, such as when the sun is too bright, for example, a lower efficiency system may actually benefit the organism, he added. "What this means for moving the energy through the biological system is one of these deep questions we're still exploring." Also in question is how widespread these quantum effects are in nature, Fleming said. The fact that photosynthesis is an extremely fast process might be "crucial" for quantum principles to have a noticeable effect, he explained. "In real terms, of course, these quantum effects don't last very long at all," but in these light-harvesting systems, where electrons are being excited and energy is transferred in just a fraction of a second, "something of physiological significance happens even faster," he said. "That's not true in most of the rest of biology."
**__Related stories:__***linkurl:Arsenic and old...photosynthesis?;http://www.the-scientist.com/blog/display/54930/
[14th August 2008]*linkurl:Did Enzymes Evolve to Capitalize on Quantum Tunneling?;http://www.the-scientist.com/article/display/15183/
[17th January 2005]*linkurl:A Quantum Leap in mRNA Quantitation;http://www.the-scientist.com/article/display/12108/
[30th October 2000]
Advertisement

Comments

Avatar of: anonymous poster

anonymous poster

Posts: 2

February 3, 2010

This is quite a change in thinking for biologists, hope there is more coming on this subject
Avatar of: David Bligh

David Bligh

Posts: 2

February 3, 2010

The observation of quantum effects in a living system is fascinating. But, let's not forget the basics of photosynthesis in the process (RE: conversion of carbon dioxide to oxygen, per the author). Carbon dioxide is converted into a simple carbohydrate by reduction, using protons from water and energy transferred via electrons. The origin of oxygen, then, is water not carbon dioxide.

February 3, 2010

\n\nJef,\n\nThis is an intriguing article. I am not a physicist and my readings on photosynthesis are in that forgotten closet where I keep things as old as the ones from twenty years ago. \n\nIt never occurred to me that matter-energy interactions of quantum mechanics could play a role in photosynthesis. I had always thought that the whole secret and power of photosynthetic organisms lied in their specific biological adaptations to maximize sun energy?s input coupled with additional specific adaptations for water use and water-saving.\n\nIndeed, another layer of complexity and integration very interesting to consider and learn. Please, keep us updated.\n
Avatar of: David Hill

David Hill

Posts: 41

February 3, 2010

Just like 'UV vision' in many animals, quantum (as opposed to classical) biophysics is a novelty that will soon be viewed as commonplace. At the small ('nano') scale of atoms and molecules, everything will behave as waveforms until these are collapsed through a technique of 'observation' that will force a particular (or particulate) result, as in 'simpler' quantum phenomena already studied. It is only a matter of time before we recognize that these waveform phenomena do not always 'cancel out' at the macro level, but can have significant 'macro results,' akin to what has come to be known as the 'butterfly effect.' At some point we will recognize that 'hard to balance' dice and 'thin-edged' playing cards represent primitive, and not completely effective, 'waveform collapsers'. We have used these devices for centuries without recognizing the simple principles by which they actually work. I am sure that the central nervous system includes some elegant 'waveform collapsers' related to our process of observation.

February 3, 2010

In the course of the complex process of plant photosynthesis , excess of sunlight may cause cellular damages. Perhaps directed energy transfer via waves might enhance cell protection.
Avatar of: anonymous poster

anonymous poster

Posts: 125

February 3, 2010

Then, they won't be too thrilled with the quantum physics of photosynthesis!
Avatar of: Warren Bonett

Warren Bonett

Posts: 1

February 3, 2010

I just hope this doesn't open the door to new wave of pseudoscience quantum hokum. I already have to field enough questions about quantum consciousness, and various versions of lipton's biology of belief.
Avatar of: Nadir Shah Khan

Nadir Shah Khan

Posts: 1

February 4, 2010

So scared of your world view being challenged?Whenever quantum is mentioned in biology your reductionist world view collapses and you start panicking.
Avatar of: Lewis Larsen

Lewis Larsen

Posts: 1

February 4, 2010

Fascinating article! Actually, very similar many-body, collective quantum effects also take place in Low Energy Nuclear Reactions (LENRs) that occur in room temperature & above condensed matter systems under just the right physical conditions. To understand how & why analogous quantum processes might operate on even higher energy-scales at STP, please go to Slide #45 in a 61-slide public PowerPoint presentation located at http://www.slideshare.net/lewisglarsen/lattice-energy-llctechnical-overviewpahs-and-lenrsnov-25-2009
Avatar of: eve barak

eve barak

Posts: 85

February 6, 2010

This comes as no surprise to me intellectually, and I am pleased -- actually delighted -- that the "physics" of biological processes is finally being addressed at the deep physical level. We need more of this kind of interaction between physics and biology, and not merely in the area of photosynthesis.\n\nFor years, I had discussions with physicists interested in studying the physics of biological systems who were looking for "interesting" systems to study. They tended to focus on things like cytoskeleton. I kept trying to convince them that a really important challenge that was crying out for physicists was the mitochondrial electron transport system that gives us oxidative phosphorylation. It's still a black box, Mitchell Hypothesis notwithstanding, and it has always been clear to me that quantum physics, or at least particle physics, was needed to really fathom what was going on at the deepest and most reductionist level of understanding. Of course, these physicists went back to their biological collaborators, who encouraged them to keep on trucking with the cytoskeleton. \n\nI sincerely hope this is the beginning of a new era in biological research, an opening-up of a whole new way that physicists look at biological systems. After all, biological systems, even at their most mysterious (e.g., Mitchell Hypothesis), obey the Natural Laws (i.e., the Laws of Physics). It's just that those laws are still being unearthed, and the modes by which biological systems obey those laws are still being deciphered.\n\n
Avatar of: Al Bradbury

Al Bradbury

Posts: 7

February 8, 2010

Firstly I was writing about quantum mechanical discoveries in photosynthesis many months ago so I dont know why its suddenly news.\n\nAgain, this is not a new discovery, physicists have talked about things which are implicitly quantum mechanical in photosystems. Capturing energy from heat or visible photons is quantum mechanical by nature.\n\nTherefore the comment on mitochondria is spot on. In fact, mitochondria appear to gain energy from heat, and it is not implausible that they were crude photosynthesisers/thermosynthesisers and chemosynthesisers when their ancestors were anaerobic photosynthetic alpha-proteobacteria.\n\nBut the dogma that you cant have room temperature entanglement is long realised (by any good thinker) to be pure hokum and it just does not check out. For example, photons in photosynthetic systems would tend to naturally involve all mannor of entanglement phenomena, as optical physicists and engineers have been discovering (look at optical sensors and computing technology). Because the ammount of energy is not great, boosting efficiency requires ensuring there are systems at the right 'energy state' to receive the quanta of energy available. A 'quantum system' computes within a large network where to put that energy, so that entropy can be directed in a fashion consistent with the fundamental property of life - the entropy generates order. This requires a system of 'entropy direction', which brings us to the following comment in this thread:\n\ncomment:\ncan quantum-based energy transfer be a mechanism of cell protection\nby mabrouk el-sharkawy\n\n[Comment posted 2010-02-03 16:21:33]\n\n"In the course of the complex process of plant photosynthesis , excess of sunlight may cause cellular damages. Perhaps directed energy transfer via waves might enhance cell protection."\n\nOf course, and thats something that must happen in ALL living systems. The genetic system and the metabolic system preserve themselves via quantum interactions. It is not only proposed on line by myself before this, it also is proposed that life has to evolve via a system of controlled entropy and that this selects for quantum mechanical properties that assist this, in the adoption of each cell molecule, especially those that are 'metabolic' because this is where the entropy is. To help define this I coin the term 'quantum selection' which means that the highest ordered structures in the cells survive against entropy only by quantum interactions that 'throw off' damaging molecular-energy interactions that would otherwise destroy these complex networks (destroy the order, which represents the cell). The complexity in life is actually fundamentally dependent on having 'quantum' properties that allows energy that is destructive to cascade through metabolic systems, which predate photosynthetic systems and are based on accelerations of natural entropy in hydrochemistry in the crust. The entropy is thereby directed by making the entropic system sacrificial but by making the ordered system selectively invisible. This again is a system requirement for life, and reflects the properties of 'quantum' materials.\n\nSo, the molecules selected by life are partly selected because they can 'cooperate' and 'hide' from entropic forces, and utilise the entropy within the cell to boost back cell repair of the complex system. This spells the ability of these components to selectively tune to each other and this process is essentially what happens on quantum mechanics. Life is based on preservation of complexity that itself cooperates to this end, so it leads to a selection of interactional, theregore ' quantum mechanical' properties in these cell components. These cell components are the order and the information and the machinery of the cell, they are entropy converters, but they must AVOID entropy themselves: the best way to do that is to have properties where interactions divert forces of entropy ie photons away from the desired ordered structures, and to use the more interactional structures as 'entropy acceptors' which in turn become the recognised bits of the metabolic system ie the electron transport chain. Quantum phenomena are essentially merely the result of given components selectively interacting (exchanging energy) to particular others. This is not caused by adding entanglement but actually by taking it away - hence, entanglement is a process of isolation and transfer, in which those 'resonant' components are able to transfer energy rapidly to each other, thereby avoiding the physical consequences of accepting the energy themselves. Quantum entanglement is essentially a preferential instantaneous 'entropy network' that reduces internal topographical changes by switching out energy, but also allows the network to ignore energy it isn't in the condition to interact with as a group, otherwise would ammount to molecular events and manifestation of fields that spread out interaction with other things. This process results in the weirdness of things like superconductors, which reject interaction with magnetic fields. Once a certain ammount of interaction is forced, quantum properties ie superconductivity, fail and fail very rapidly through heating and conformational changes in the material. Below that threshold the behavior looks weird and magical, because the entanglement is actually selective and more limited (but more effective at transfering energy) than in the surrounding non-weird materials which we model as classical, and which are not 'living'. \n\nAnd, this ability to select out things that dont interact with the 'group', unless the interaction is suitably violent, is based on the properties of the group 'members' to interact in such away to move entropy away. This means that in evolving materials, where order is to increase in spite of the energy, there is a need for each component to be selected in terms of its ability to assist this cooperation and this means its quantum mechanical abilities and its cooperation are intrinsically related and are increasing properties in any evolving system of this type.

Follow The Scientist

icon-facebook icon-linkedin icon-twitter icon-vimeo icon-youtube
Advertisement

Stay Connected with The Scientist

  • icon-facebook The Scientist Magazine
  • icon-facebook The Scientist Careers
  • icon-facebook Neuroscience Research Techniques
  • icon-facebook Genetic Research Techniques
  • icon-facebook Cell Culture Techniques
  • icon-facebook Microbiology and Immunology
  • icon-facebook Cancer Research and Technology
  • icon-facebook Stem Cell and Regenerative Science
Advertisement
Advertisement
Life Technologies