Quantum Biology: The Physics Driving Biological Systems

In June 2015, nuclear physicist Dr. Jim Al-Khalili presented a TED Talk entitled “How quantum biology might explain life’s biggest questions” (watch video here). This new scientific field is transforming the established paradigms of chemistry and biology by integrating quantum theory principles. In a few short years, quantum biology has already revolutionized our understanding of large-scale animal migrations, photosynthesis, and cancer-causing mutations.

Before answering these questions, we should start by answering the question, what exactly is quantum physics? In the movie “The Theory of Everything,” Steven Hawking’s wife Jane (played by Felicity Jones) compares the quantum world and the “big world” of general relativity by using peas and potatoes as examples. If the universe were only made up of planets (potatoes), then the mathematics behind planetary movement and universal expansion would be fairly straightforward. After all, Aristotle, and later Ptolemy, both devised theories of how the universe was organized beginning in the 4th century. Mankind has sought to understand the heavens since the time of the ancients. Therefore, humans have had hundreds of years to determine the physics that governs planetary movement and our cosmological position amongst trillions of other stars and galaxies. However, the universe is not composed solely of planets. It also contains very small atoms and subatomic particles (peas), which play by a completely different set of rules. It is only recently that researchers have begun to understand this strange quantum world and only more recently still that the quantum field has begun to expand out of physics into the newly developed field of quantum biology.

Photo Credit: National Aeronautics and Space Administration (NASA)

Physics has always been a bit of a loner on the scientific front. While biology and chemistry have an easy marriage in scientific literature, biological systems were long deemed too complex for physics. Additionally, while the small world of chemical reactions and atomic bonds can simply be scaled up from molecular biology into its “big world” cousins of ecology, anatomy, botany, etc., physics either deals with the very small or the very large, and the mathematics behind each scale are so colossally different as to constitute two clearly divided sub-fields. Which begs the question, where does the world of “intermediate,” human-sized objects fit?

The emerging field of quantum biology seeks to answer this question by integrating quantum physics principles into established biological and chemical theories, thus answering some of biology’s greatest questions. So at the smallest scale, physics dictates how subatomic particles move and interact. These form atoms, which create molecules, which are studied by organic chemists. Finally, at the largest scale we have organs, organ systems and organisms. According to Dr. Al-Khalili, the quantum physical processes of quantum tunneling, quantum coherence and quantum entanglement have all been shown to influence larger biological processes.

European robin

Photo credit: Francis C. Franklin [Public Domain], Via Wikipedia Commons

Perhaps the most interesting example comes from the migration route of the European robin (Erithacus rubecula). Like many other birds, the European robin migrates in the fall from the frigid climate of Scandinavia to the temperate respite of the Mediterranean by following the Earth’s magnetic field. Despite this field being incredibly weak (nearly 100x weaker than the magnetism displayed by a refrigerator magnet), somehow the birds are able to hone in on the signal and unerringly follow it to their winter-feeding destinations. A 2011 study suggests that a protein inside the retina of the bird’s eye contains electrons that are quantum entangled. This means that despite being physically separated, the electrons are linked in a quantum manner that has yet to be determined. A photon of light hitting the bird’s retina causes one of these spatially separated electrons to “spin” in a way that depends on its orientation to the Earth’s magnetic field. The interaction of the two entangled electrons produces a chemical signal that guides the bird south, like an entanglement-based compass.

Quantum tunneling is similar to throwing a baseball against a wall and having the ball actually pass through the wall, rather than falling to the ground. This is a well-documented phenomenon of electron movement, particularly in enzymes (see Masgrau et al. 2006). The electron essentially acts as a wave, rather than a particle, with a certain probability of being able to pass through an impenetrable barrier. Thus it is able to change its position within a molecule, “tunneling” from one location to another. In enzymes, this serves to accelerate certain cellular reactions. However, quantum tunneling can also cause DNA mutations. Nucleotides are held together by a double hydrogen bond, which allows protons to hop from one nucleotide to the other, like a person crossing a bridge. If the bond is broken during DNA replication while the proton is on the “wrong” nucleotide mutations can occur in the genetic material, potentially leading to cancerous growth.

Another quantum biological process known as quantum coherence has been found to aid in photosynthesis (see Lambert et al. 2013 for review or Engel et al. 2007). When green-sulfur bacteria harvest photons of light, the energy is transferred to a specialized reaction center called the Fenna-Matthews-Olson (FMO) complex with nearly 100% efficiency. This level of efficiency is only capable through quantum coherent energy transfer, where the photons behave like a wave, spreading outwards and following multiple pathways to the FMO complex. In this way, light energy finds the optimal pathway to the reaction center without dissipating as heat.

Quantum biology, an entire sub-field I was unaware of prior to Dr. Al-Khalili’s talk, has already made invaluable strides to elucidate the mechanisms responsible for some of life’s greatest mysteries. The many quantum biology papers featured in magazines such as Science and Nature show exactly how influential this new field is and how many researchers are taking notice. It’s highly likely that quantum biology will continue to unravel many features of organismal physiology that have yet to be adequately explained by our current understanding of biological and chemical processes.

-Victoria Barker

Literature Cited

Engel, Gregory S., et al. “Evidence for wavelike energy transfer through quantum coherence in photosynthetic systems.” Nature 446.7137 (2007): 782-786.

Gauger, Erik M., et al. “Sustained quantum coherence and entanglement in the avian compass.” Physical Review Letters 106.4 (2011): 040503.

Lambert, Neill, et al. “Quantum biology.” Nature Physics 9.1 (2013): 10-18.

Masgrau, Laura, et al. “Atomic description of an enzyme reaction dominated by proton tunneling.” Science 312.5771 (2006): 237-241.

Advertisements

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s