Can Quantum Mechanics Explain Biology?

[Karl G.]

In my biology class, I've learned that most of the fundamental processes of genetics occur on an atomic level (i.e. DNA, RNA, etc.). Can quantum mechanics be applied?

 

[alxm]

In my biology class, I've learned that most of the fundamental processes of genetics occur on an atomic level (i.e. DNA, RNA, etc.). Can quantum mechanics be applied?

It can and is, in the sense that all chemistry is inherently quantum. There are no 'classical' atoms, so to speak.

Then there's of course the field of Quantum Chemistry (a part of theoretical chemistry/physical chemistry/chemical physics), which naturally involves quantum mechanics directly, either by solving the Schrödinger equation, or using density-functional theory (which is essentially a reformulation of the Schrödinger equation, although most DFT methods used now are somewhat 'semi-empirical' ) However, quantum mechanical calculations of molecular systems are computationally expensive, limited to about 100-200 atoms or so. Which isn't to say that biochemical systems aren't studied using model systems though. (e.g. while enzymes are huge, the 'active site' where the actual reaction occurs isn't very large)

If you're wondering whether there are are purely 'quantum' effects involved (as opposed to 'chemical' effects), there isn't much. Tunneling is important for electron-transfer kinetics. The effect of proton tunneling has been measured in some very accurate kinetics studies, but it's really just barely measurable in the best of circumstances.

 

[George Jones]

In my biology class, I've learned that most of the fundamental processes of genetics occur on an atomic level (i.e. DNA, RNA, etc.). Can quantum mechanics be applied?

Some researchers think that quantum (entanglements) effects are responsible for biological effects at much larger scales. See

http://discovermagazine.com/2009/feb/13-is-quantum-mechanics-controlling-your-thoughts,

from which it should be possible to look up more rigorous references.

 

[alxm]

Some researchers think that quantum (entanglements) effects are responsible for biological effects at much larger scales.

Nothing in that article talks about any large-scale effects of quantum entanglements. And there is no evidence supporting that.

In general, you're not going to see any large-scale entanglement in a biological systems. The decoherence time is far too short. (the wild and speculative claims of "quantum consciousness" fans from Penrose to Deepak Chopra notwithstanding).

Besides which, if there were any significant such effects, it's much much more likely that they would have been discovered already within inorganic or organic chemistry, which are both far more mature fields that have the added benefit of working at a smaller scale.

There is no 'gap' in knowledge, no big unexplained phenomenon, between chemistry and quantum physics or between biochemistry and other chemistry.

 

[George Jones]

Nothing in that article talks about any large-scale effects of quantum entanglements.

The article uses the word "entanglement" three times, and most certainly does imply what I wrote, i.e., that some researchers (besides Hameroff) think that quantum effects are responsible for biological effects at larger scales than in the original post in this thread. For example, the article starts with "Graham Fleming,"

http://chem.berkeley.edu/faculty/fleming/index.html, and,

looking at the projection operators in Fleming's technical articles, it seems to me that Fleming is invoking quantum entanglement to explain photosynthesis.

The article also talks about the role which some researchers believe quantum tunneling plays in some biological processes.

Note that I did not say that I believed all this (I expressed much skepticism to my wife upon first seeing the article), nor did I say that these were conventional positions. I don't know enough to make that call.

 

[alxm]

looking at the projection operators in Fleming's technical articles, it seems to me that Fleming is invoking quantum entanglement to explain photosynthesis.

And that's valid work, but also entirely unrelated to biological systems specifically. The transfer of vibrational states in any (chemical) systems is simply not something that's been studied much until the very recent advent of femtosecond spectroscopy. This is not an example of a quantum effect on a macro (molecular) scale, an effect unique to biochemistry, or something just fundamentally different from 'chemistry as we know it'. It's more that photosynthesis was/is an important and interesting system to study.

The article also talks about the role which some researchers believe quantum tunneling plays in some biological processes.

Which is a silly angle to put on it. Electron transfer plays an important role in quite a few biological processes. I already mentioned tunneling effects are quite important to electron-transfer kinetics. Again, it's not something unique to biochemistry.

Note that I did not say that I believed all this (I expressed much skepticism to my wife upon first seeing the article), nor did I say that these were conventional positions. I don't know enough to make that call.

Well, the work cited there does seem mostly legit (although the subheading makes reference to 'quantum consciousness' which I think is more or less crackpottery). It's just that the journalist seems to put a silly angle on it. It bears repeating: Everything in chemistry is quantum in nature. And like all chemistry, biochemical systems can be studied and explained most accurately in quantum-mechanical terms. And there are plenty of problems in biochemistry for quantum chemists to solve.

OTOH, what I do say is that there's nothing in biochemistry that involves truly 'macroscopic' quantum effects, and that the quantum mechanical explanations that do explain biochemical phenomena are never going to be unique to biochemistry. At least not on the fundamental level. The molecules may be bigger, reactions may have more steps, but they're not fundamentally different.

 

[alxm]

Just as a side note, I think it's more fun when biological systems work 'against' the Rules of Quantum Mechanics.

I don't remember the enzyme, but there's at least one that catalyzes an apparently spin-forbidden reaction, by creating tyrosine radical as an intermediate. By doing so it isolates the electron involved in the reaction, allowing it to flip its spin.

It's quite cute.

 

[Karl G.]

Another question: is it possible QM will be ever used in the theory of evolution?

 

[QuantumBend]

Another question: is it possible QM will be ever used in the theory of evolution?

Evoultion is Biologicals - Darwin BUT QM is physics and mathematics.

 

[alxm]

Another question: is it possible QM will be ever used in the theory of evolution?

It already is, in the sense that evolution can be explained in terms of biochemistry, which is explained by chemistry, which is explained by QM.

QM isn't likely to play a direct role in explaining evolution. Not any more than QM would be used in the theory of the motion of billiard balls.
In other words, you can use QM to explain evolution/billiard balls, but there's no reason to do so.

 

[Karl G.]

Yes - come to think of it, evolution is (usually) to macroscopic to even remotely consider the effects of QM - but the possibility that quantum mechanical effects could give rise to properties of life we see is intriguing

 

[QuantumBend]

Yes - come to think of it, evolution is (usually) to macroscopic to even remotely consider the effects of QM - but the possibility that quantum mechanical effects could give rise to properties of life we see is intriguing

This mean nothing then quantum in ALL atom and cell. It always do things all times - so no good.

 

[nikman]

Another question: is it possible QM will be ever used in the theory of evolution?

The Apostle of Quantum Evolution has to be Johnjoe McFadden, a molecular biologist at the U of Surrey who also writes occasional pop science columns for The Guardian. Also he disagrees with Hameroff's quantum description of brain function, but has his own.

Unfortunately (IMO) he muddies the water by dragging in multiverse theory. But it's still interesting stuff:

http://www.surrey.ac.uk/qe/
Coming closer to earth, there's a lot of fascinating stuff at the University of Illinois at Urbana-Champaign / Theoretical and Computational Biophysics Group's website:

http://www.ks.uiuc.edu/Research/Categories/Quantum/all.cgi
Good paper from last year on quantum effects in avian magnetoreception (or, how birds manage to navigate all over hell and gone):

http://arxiv.org/abs/0804.2646

 

[QuantumBend]

The Apostle of Quantum Evolution has to be Johnjoe McFadden, a molecular biologist at the U of Surrey who also writes occasional pop science columns for The Guardian. Also he disagrees with Hameroff's quantum description of brain function, but has his own.

Unfortunately (IMO) he muddies the water by dragging in multiverse theory. But it's still interesting stuff:

http://www.surrey.ac.uk/qe/

This theory NOT prooved, not good for University to make it. Better science FICTION - yes, no good.