Can quantum phenomena explain biological processes?

Pavan Thilagaraj

Can Quantum Phenomena explain Biological Processes?

An Extended Project by Pavan Venkatesh Thilagaraj

Of d’Overbroeck’s, Oxford

Supervised by Mr. Adam Johnstone

Table of Contents

IntroducJon 2 ..................................................................................................................................................

Darwin’s Theory of EvoluJon 2 ........................................................................................................................

Quantum Physics 3 ..........................................................................................................................................

Wave-ParJcle Duality of Light 3 ..................................................................................................................

Quantum Coherence 5 ................................................................................................................................

Quantum Entanglement 5 ...........................................................................................................................

IntroducJon to Quantum Biology 9 .................................................................................................................

Enzyme Efficiency – The Need for New Models 9 ...........................................................................................

Avian MagnetorecepJon 11 ............................................................................................................................

Photosynthesis 14 ...........................................................................................................................................

OlfacJon 15 .....................................................................................................................................................

Consciousness 17 ............................................................................................................................................

Conclusion 18 ..................................................................................................................................................

Bibliography 20................................................................................................................................................

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Introduc8on Before the advent of Quantum Theory, ScienJsts regarded Classical Physics as absolute and assumed that Classical Physics should hold true for extremely small objects such as atoms and electrons. However, Classical Physics could not explain what the experiments with these fundamental parJcles suggested and so, the need of a new pertaining theory was required – Quantum Theory.

Considering that classical modellings of Biological Processes such as Photosynthesis cannot explain the process’ efficiency , it would make sense to turn to Quantum Physics for help. The reason for applying 1

Quantum Physics becomes even sounder when one sees that biological processes involve microscopic interacJons of electrons, atoms and slightly larger molecules, all of which must be governed by the rules of Quantum Physics.

I will first introduce the required fundamental ideas of quantum mechanics and biology, which I will then use to explain quantum biological models, as well as their feasibility and reliability.

Darwin’s Theory of Evolu8on

Before we jump into Quantum Physics, let’s establish some ground facts. The theory of evoluJon proposed by Charles Darwin in the early 19th century was the most controversial theory of its Jme. EvoluJon Theory is widely appreciated in the scienJfic community now , and is largely evidenced by 2

fossils and radiocarbon daJng with all evidence favouring Darwin’s evoluJon theory. It involves a simple 3

but smart concept.

All living Organisms contain some form of gene that codes for the organism’s characterisJcs – structural, behavioural, metabolism and so on. These genes (or some of the genes) are always passed down to the organism’s offspring. Suppose we had two bacteria of the same species – A and B. Both bacteria are in an environment of sustaining nutriJon but are exposed to anJbioJcs. In such a case, we would call the ‘Selec8on Pressure’, the anJbioJc. Bacteria A is lucky, and possesses adaptaJons due to its genes which provide Bacteria A with resistance towards this anJbioJc – Bacteria A is ‘Selected for’. While Bacteria B does not possess any beneficial adaptaJons against this anJbioJc – Bacteria B is ‘Selected Against’. Due to this, Bacteria B dies out and is unable to pass on its genes, however, Bacteria A survives and can pass on its genes. In other words, organisms that have beder suited adaptaJons to their environment will survive and pass on their genes.

This is basically Natural Selec8on. One should know, that these differing genes are brought about by random geneJc mutaJons. Through conJnuous Natural SelecJon over successive generaJons, organisms develop different traits that deviate from the normal range of traits. This causes the formaJon of new species and evoluJon.

RelaJng towards Quantum Physics, Natural SelecJon could lead to organisms that make use of Quantum Processes by aiding and ‘stabilising’ them (as we will see later). Considering that Quantum Processes are much more efficient than Classical Processes, it would make sense that organisms which maintain or aid

Edward O’Reily and Alexandra Olaya-Castro, ‘Non-classicality of the molecular vibraJons assisJng exciton energy transfer at 1

umbroom temperature', Nature Communica.ons <hdp://www.nature.com/arJcles/ncomms4012> [accessed July 12th, 2016].

Theodosius Dobzhansky, ‘Nothing in Biology Makes Sense Except in the Light of EvoluJon’, the American Biology Teacher, vol. 2

75, no. 2 (2013), pp. 87-91.

Richard Dawkins, The Blind Watchmaker (New York: Addison-Wesley, 1989), p.316-317.3

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these Quantum Phenomena would be Selected For (as they are more efficient) over those organisms that may not aid Quantum Phenomena as much.

Quantum Physics Short and concise, “Quantum theory is the theoreJcal basis of modern physics that explains the nature and behavior of mader and energy on the atomic and subatomic level. The nature and behavior of mader and energy at that level is someJmes referred to as quantum physics and quantum mechanics.” 4

The first hint towards Quantum theory to scienJsts was realizing that certain parJcles possessed quanJsed properJes. For a quanJty to be quanJsed, the quanJty must only be able to increase in discrete packets and cannot be conJnuous. A nice example of discrete quanJJes would be shoe size, which can only increase in regular increments – you cannot have a shoe size in between 7 and 8, such as 7 and a half. Max Planck was the first to propose that radiaJon was quanJsed . Albert Einstein then 5

followed, demonstraJng that light energy was also quanJsed (through a demonstraJon now called the photoelectric effect). Another scienJst, Robert Millikan demonstrated that electric charge was quanJsed (through an experiment now called Millikan’s oil drop experiment ). 6

Wave-ParJcle Duality of Light As the photoelectric effect demonstrates that light is quanJsed, it can also be interpreted as ‘light is made from parJcles’ (recall, that the photoelectric effect shows that light is discrete). However, experiments such as Young’s Double Slit experiment resulted in light behaving exactly as how a wave. In the Double Slit experiment, light was made to pass through two slits. The emerging light would then form a padern on a viewing screen. Per the photoelectric effect, light is a parJcle so the padern produced is supposed to be just as the figure given below.

Margaret Rouse, ‘What is Quantum Theory?’, What Is <hdp://whaJs.techtarget.com/definiJon/quantum-theory> [accessed 4

July 15th, 2016].

Susan Lafo, ‘Quantum Theory Timeline’, Par.cle Adventure <hdp://www.parJcleadventure.org/other/history/quantumt.html> 5

[accessed 4th July, 2016].

Gurinder Chadha, A Level Physics for OCR: Millikan’s Experiment – The Discovery of Quan.sa.on of Charge (Oxford: Oxford 6

University Press, 2015), p.120 – p.121.

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7

Figure 1 – The padern produced if light acted as a parJcle

However, the actual result was the padern on figure 2. This padern supports the idea of light being a wave, and not a parJcle. The padern produced on the viewing screen is now called an interference paKern.

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Figure 2 – The interference padern produced if light acted as a wave

This interference padern would be produced by any wave such as water waves or sound waves. The padern is produced due to the different interacJons of the diffracted light waves with each other. When the crest of one wave meets the crest of another wave, it produces a bright line on the screen (they produce an amplified wave). When the crest of one wave meets the trough of another wave, it produces no line on the screen (they cancel out).

ScienJsts conducted this experiment using a single ‘parJcle’ of light (the smallest light energy possible to be sent through the slits) yielding the same results as figure 2. The scienJsts sent one parJcle of light at

Bryan Clintberg, ‘Young’s Double Slit Experiment’, Study Physics <hdp://www.studyphysics.ca/newnotes/20/unit04_light/7

chp1719_light/lesson58.htm> [accessed 4th July, 2016].

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a Jme through the slit. Somehow, each individual parJcle interacted with itself to produce the same padern in the end. This wave-parJcle duality holds true for other fundamental parJcles, as well. 8

In such a sense, light acts as a both, a parJcle and a wave but its behavior changes as per the experiment you decide to conduct with it. In other words, unJl you measure its nature through experimentaJon, it is superposed as a wave and a parJcle. The mathemaJcs behind it talks in terms of probability but is not required to be learnt to understand this topic.

Another point to add is that wave-parJcle duality has also been shown true for mader – ‘parJcles’ such as electrons, atoms and even larger molecules, such as fullerenes. In other words, parJcles on the 9

atomic scale can also display interference paderns with the same experiment. All mader should be able to behave as a wave but this effect of duality is quickly dissipated by decoherence.

Quantum Coherence If two parJcles vibrate in unison, the parJcles display quantum coherence and they can now interact with one another as waves to form the previously discussed interference paderns. However, in macroscopic objects, this process is cancelled out by quantum decoherence due to the random moJon of all parJcles within the object. It is also possible for a single parJcle to cohere with itself, if it is 10

unaffected or ‘shielded’ from any other molecular vibraJons.

It can also be noted that Quantum Coherence can occur in any system with the same vibraJon. This means that if a system were to be cooled to absolute zero, no mader how large, that system would be displaying Quantum Coherence (as all parJcles in that system have no vibraJon). In other words, the parJcles’ “once-chaoJc movement becomes almost choreographed in smooth lidle waves” 11

Quantum Entanglement Quantum Entanglement is a phenomenon which occurs when a pair, or a group, of parJcles are formed and interact with one another in such a way that the state of a single parJcle in the system cannot be described independently but can only be described for the enJre system.

To understand this phenomenon beder, here is a simple example of Quantum Entanglement – Consider two glass panes of different colours, glass pane A and glass pane B. It is known that when the glass panes are aligned together, they create a magenta colour. Suppose that one glass pane is red, we can then confirm that the other glass pane will be blue. If glass pane A was red, then, glass pane B would have to be blue. It is, however, impossible to predict the state of either of these glass panes beforehand.

This is the same principle seen in electron pairs (electrons with the same energy levels). The direcJon of spins in the system add up to zero. Hence, one of the electrons may have a counter-clockwise spin, or a clockwise spin and is therefore considered to have both spins unJl it is measured, auer which the

Andrew May, ‘Quantum Double-Slit’, in 30-Second Quantum Theory, ed. by Brian Clegg (London: Icon Books Ltd, 2014), pp. 32.8

Olaf Nairz, Björn Brezger, Markus Arndt, and Anton Zeilinger, ‘DiffracJon of Complex Molecules by Structures Made of Light’, 9

Universitat Wien <hdps://www.univie.ac.at/qfp/research/maderwave/stehwelle/standinglightwave.html> [accessed 3rd July, 2016].

Michio Kaku, Physics of The Impossible –A scien.fic Explora.on of The World of Phasers, Force Fields, Teleporta.on and Time 10

Travel (London: Penguin Books, 2009), p.60-61.

Brian Madmiller, ‘once-chaoJc movement becomes almost choreographed in smooth lidle waves’, University of Wisconsin-11

Madison <hdp://news.wisc.edu/physics-team-studies-atomic-life-at-absolute-zero/> [accessed 8th July, 2016].

Page � of 205

parJcles are ‘forced’ into a single spin. The rule sJll stands however, that both electrons must have 12

opposing spins regardless of the distance between them. In addiJon, just to note, a pair of electrons with opposite spins is called a singlet pair while a pair of electrons with the same spin is called a triplet pair. 13

Do note however, that the state or spin of the parJcle can change auer ceasing measurement or observaJon and the parJcle will remain entangled regardless.

Quantum Tunneling

Quantum Tunneling is a quantum phenomenon where parJcles tunnel through an energy barrier which they could not classically overcome. This means there is a probability for reactants of insufficient energy to overcome the energy requirements in a reacJon and ‘tunnel’ across to the other side. This probability decreases as the size of the parJcle increases (it is harder for larger parJcles to quantum tunnel).

To get an understanding of how important quantum tunneling is in physics, it is the only mechanism that can explain how nuclear fusion is possible in stars. 14

Stuart Hamero, ‘That’s Life! – The Geometry of Electron Clouds’, in Quantum Aspects of Life, ed. by Derek Abbod, Paul Davies 12

and Arun PaJ (London: Imperial College Press, 2008), pp. 403-432: 423-424.

David Griffiths, Introduc.on to Quantum Mechanics (New Jersey: PrenJce Hall, 1995), p. 165.13

David Weintraub, How Old Is the Universe? (Oxford: Princeton University Press, 1958), p. 37.14

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Figure 3 – A comparision of parJcle nature to wave nature Source: University of Oregon <h]p://abyss.uoregon.edu/~js/glossary/quantum_tunneling.html>

The kine8c isotope effect (KIE) is the decrease of the reacJon rate due to an atom in a reactant being subsJtuted with its heavier isotope. Quantum Tunneling provides the basis for the KIE. Moreover, if 15

there is any reacJon which follows the KIE, we can almost be certain that Quantum Tunneling plays a role in that reacJon.

Quantum Tunneling also provides the basis of a spectroscopy known as Inelas8c Electron Tunneling Spectroscopy (IETS). In IETS, an electron is made to tunnel from a ‘donor’ molecule to a ‘recipient’ molecule through a ‘buffer’ molecule. However, the electron is only allowed to tunnel to an area in the recipient molecule with the same energy level (elas8c). If the area in the recipient molecule has a lower energy level, the electron must give out some of its excess energy to the intermediate molecule before proceeding to the recipient molecule (inelas8c).

To be more specific, the electron gives its excess energy to the bonds of the buffer molecule. The energy that a bond can accept depend upon the bond’s vibraJon which can be influenced by heavy isotopes (heavier elements reduce the vibraJon of a bond). This means that electron tunneling can only occur if the correct buffer molecule is available.

Vranken, D. [UCI Open]. (2014, March 20th). Chemistry 202. Organic Reac.on Mechanisms II. Lecture 21. Kine.c Isotope 15

Effects, [Video File]. Retrieved from <hdps://www.youtube.com/watch?v=n-FdeOSdQX0>.

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Hence, in IETS, it is possible to differenJate between molecules by detecJng whether the electron has tunneled and detecJng the energy difference between the donor and recipient molecules. IETS is important as it is a concept we will use later.

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Introduc8on to Quantum Biology Having reviewed Quantum Physics and basic biological knowledge, I will now present various case studies of biological processes, linking each process to its widely accepted Classical model, and to its Quantum model. I will link the efficiency of enzymes to quantum tunneling, Avian MagnetorecepJon to Quantum Entanglement, Photosynthesis to Quantum Coherence, and OlfacJon to InelasJc Electron Tunneling Spectroscopy within Quantum Tunneling.

Enzyme Efficiency – The Need for New Models Prior biological processes such as enzyme (biomolecules that increases a reacJon’s rate) acJon are normally explained through classical models. Enzyme acJon is believed to work through the Transi8on State Theory (TST). It assumes that, “there exists an intermediate configuraJon of the reactants at which the potenJal energy has a maximum value. This state is referred to as the transi8on state”. Hence, the 16

reactants must possess sufficient energy to overcome the reacJon’s ac8va8on energy to form the transiJon state, and must collide with another reactant in the correct orientaJon to do so.

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Figure 4 – Graph of the free energy of molecules in a system against the course of the reacJon

Enzymes are believed to accelerate the many metabolic reacJons of life by stabilising the transiJon state (intermediate state) and thus, reducing the acJvaJon energy required by the reactants to react. But, classical models of random reactant collisions (using Collision theory and TST) fail to explain the efficiency that enzymes provide. 17

Keith Laidler, ‘TransiJon-state theory’, Encyclopaedia Britannica, <hdps://www.britannica.com/science/transiJon-state-16

theory> [accessed 3rd July, 2016].

Jim Al-Khalili and Johnjoe McFadden, Life on the Edge: The Coming Age of Quantum Biology - The Engines of Life (London: 17

Transworld Publishers, 2014), p. 84.

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However, models using Quantum phenomena can explain these effects. Any calculated theoreJcal reacJon rate involving only classical TST and excluding quantum tunneling effects would be much lower from the actual reacJon rate, evidencing that quantum tunneling is a reality. 18

Personally, the fact that certain classical models of Biology could explain the observed results, reminds me of when physicists could not explain the photoelectric effect using classical physics and had to proceed towards quantum physics. In such a sense, perhaps quantum physics is exactly what these models need.

Enzymes increase the rate of a reacJon by reducing the energy required by the reactants to adain a transiJon state. For an enzyme to act on a substrate (the substance that an enzyme acts on), the substrate, which moves randomly, must collide in the correct orientaJon to a specific part of the enzyme – its ac8ve site (the region that a substrate binds to in enzymes). The reacJon then occurs once the substrate is fit into the acJve site, with the enzyme then releasing the products.

Lactate dehydrogenase (LDH) is an enzyme found in nearly all living cells. LDH acts on a molecule called

NAD+ to NADH or the other way around. LDH is one of many enzymes that must transfer a hydrogen

atom in this process and quantum biologists believe that the hydrogen is transferred through quantum tunneling – hydrogen tunneling. Hydrogen tunneling has also been detected in biological systems with another enzyme, alcohol dehydrogenase (ADH), at room temperature (25°C) and at higher temperatures of 65°C. ADH is also related in a process involving hydrogen transfer. 19

The above just implies that hydrogen tunneling and hydrogen transfer reacJons show a correlaJon with the KIE being measured to test the presence of Hydrogen tunneling in these enzymes. This is a fair 20

method of measurement as the KIE states that reacJon rate falls due to the use of heavier isotopes. Quantum tunneling is also harder to achieve with increasing masses (heavier isotopes). Thus, there is a correlaJon between the KIE and hydrogen tunneling.

Another evidence for the involvement for quantum tunneling in enzyme processes is the fact that, classical TST cannot explain why the reacJon rate remains constant at temperatures below 100°K . At 21

very low temperatures, substrates lack the energy required to achieve a transiJon state. The fact that reacJons occur at such low temperatures suggest the involvement of the substrates tunneling across this energy gap. Another experiment also evidences this by changing the pressure, rather than the temperature. 22

Takayuki Fueno, ‘TransiJon State TheoreJcal CalculaJons of the Canonical Rate Constants for Bimolecular ReacJons’, in 18

Transi.on State: A Theore.cal Approach, ed. by Takayuki Fueno (Tokyo: Kodansha, 1999), pp.65-86: 82-83.

Amnon Kohen et al., ‘Enzyme Dynamics and Hydrogen Tunneling in a Thermophilic Alcohol Dehydrogenase’, Nature <hdp://19

www.nature.com/nature/journal/v399/n6735/abs/399496a0.html> [accessed July 10th, 2016].

Judith Klinman and Amnon Kohen, ‘Hydrogen Tunneling Links Protein Dynamics to Enzyme Catalysis’, Na.onal Center for 20

Biotechnology Informa.on <hdps://www.ncbi.nlm.nih.gov/pmc/arJcles/PMC4066974/> [accessed July 10th, 2016].

Don DeVault and Bridon Chance, ‘Studies of Photosynthesis Using a Pulsed Laser’, Na.onal Center for Biotechnology 21

Informa.on <hdp://www.ncbi.nlm.nih.gov/pmc/arJcles/PMC1368046/> [accessed July 10th, 2016].

Sam Hay, ‘PromoJng MoJons in Enzyme Catalysis Probed by Pressure Studies of KineJc Isotope Effects’, Na.onal Center for 22

Biotechnology Informa.on <hdps://www.ncbi.nlm.nih.gov/pmc/arJcles/PMC1766415/> [accessed July 10th, 2016].

Page � of 2010

One may argue that the KIE can be explained in terms of classical models but even then, theoreJcal studies have shown that the measured KIE is caused majorly by quantum tunneling. 23

However, other theoreJcal studies show that quantum tunneling does not contribute to the overall reacJon in biological systems with another enzyme, lipoxygenase. Moreover, a scienJst, Finke, also 24

showed that there is no significant difference in the KIE regardless of whether enzymes were present or not. These contrasJng findings make it uncertain that quantum tunneling is involved in certain enzyme 25

processes.

Avian Magnetorecep8on In 1975, two scienJsts, John Emlen and his son, Stephen Emlen created an apparatus called the Emlen Funnel where “a bird is placed in a circular cage with an ink pad on the bodom and paper-covered sloping walls. The cage is covered with a screen and placed in a planetarium or exposed to the sky”. 26

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Figure 5 – An Emlen Funnel Source: iPon <h]ps://ipon.hu/elemzesek/a_vorosbegy_esete_a_faraday_kalitkaval/2123/>

The scienJsts could then apply magneJc fields around the chamber and observe, through the bird’s ink imprints on the paper, the direcJon in which the birds would be most likely to fly in. It was found that the birds were sensiJve to the direcJon of the north-south components as well as the inclinaJon of the

Agnieszka Dybala-Defratyka et al., ‘Quantum Catalysis in Enzymes’, in Quantum Tunnelling in Enzyme-Catalysed Reac.ons, ed. 23

by Nigel Scrudon and Rudolf Alleman (Cambridge: RSCPublishing, 2009), pp.36-67: 61-62.

Mats Olsson, ‘SimulaJons of the Large KineJc Isotope Effect and the Temperature Dependance of the Hydrogen Atom 24

Transfer in Lipoxygenase’, Na.onal Center for Biotechnology Informa.on <hdps://www.ncbi.nlm.nih.gov/pubmed/14995199/> [accessed July 10th, 2016].

Mark Greener, ‘Did Enzymes Evolve to Capitalize on Quantum Tunneling?’, TheScien.st <hdp://www.the-scienJst.com/?25

arJcles.view/arJcleNo/16156/Jtle/Did-Enzymes-Evolve-to-Capitalize-on-Quantum-Tunneling-/> [accessed July 10th, 2016].

Hugh Dingle, Migra.on – Methods For Studying Migra.on (Oxford: Oxford University Press, 2014), p. 66.26

Page � of 2011

magneJc field. This test had proven that birds use magneJc fields to navigate, unfortunately, the 27

mechanism of how birds begin doing this was unknown.

ScienJsts had originally thought that birds had detected magneJc fields using magneJte crystals in their beaks. This is a plausible idea considering that birds have difficulty in navigaJng when magnets are 28

adached to their beaks. However, it was found that these magneJte crystals were present in macrophages for immune funcJons in the bird beak and were not related to neurons (nerve cells) or any receptors in anyway. 29

It was found however, that chemical reacJons involving free radical intermediates are influenced by magneJc fields, which can alter the product distribuJon. This is also interpreted as the radical pair 30

mechanism which is “the only well-established way an external magneJc field influences a chemical reacJon”. How the mechanism works is as follows – 31

The outermost electron pair of a molecule is quantum entangled in a singlet state (each electron in the pair have opposite spins). When the molecule is broken down into free radical components, one of the electrons in the pair may change its spin. The two electrons are sJll quantum entangled and are in a superposiJon of triplet and singlet states based upon whether the electrons have changed their spins. Moreover, this singlet or triplet state is influenced by weak magneJc fields such as the Earth’s. Hence, the chemical nature of the final products formed will be different.

‘The MagneJc Sense: The Bird’s Novel NavigaJon Mechanism’, Darthmouth Undergraduate Journal of Science <hdp://27

dujs.dartmouth.edu/2011/05/the-magneJc-sense-the-birds-novel-navigaJon-mechanism/#.V62IUJgrKUk> [accessed July 10th, 2016].

Michael Hopkin, ‘Homing Pigeons Reveal True MagneJsm’, Nature <hdp://www.nature.com/news/2004/041122/full/28

news041122-7.html> [accessed December 14th, 2015].

Christoph Treiber et al., ‘We sJll don’t know how birds navigate’, Inspiring Science <hdp://inspiringscience.net/2012/04/17/29

we-sJll-dont-know-how-pigeons-navigate/> [accessed December 13th, 2015].

Christopher Rodgers, ‘MagneJc Field Effects in Chemical Systems’, De Gruyter <hdp://www.degruyter.com/view/j/pac.30

2009.81.issue-1/pac-con-08-10-18/pac-con-08-10-18.xml> [accessed July 8th, 2016].

Klaus Schulten et al., ‘SeperaJon of photo-induced radical pair in cryptochrome to a funcJonal criJcal distance’, Nature 31

<hdp://www.nature.com/arJcles/srep03845> [accessed July 10th, 2016].

Page � of 2012

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Figure 6 – The European Robin, the mascot bird for Quantum Biology Courtesy of Nicole Bouglouan <h]p://www.pbase.com/nicolebouglouan/european_robin>

Thus, if one assumes this process to occur within a European Robin, the state of these free radical molecules can affect the chemical reacJons they induce within the cell and ulJmately, the signals transmided to the brain. This mechanism is a suitable mechanism for the way birds use the Earth’s 32

magneJc field to navigate.

The leading theory (based on the radical pair mechanism, by Thorsten Ritz) is that this molecule is the protein, ‘Cryptochrome’ present in the eyes of the European Robin. Cryptochrome forms free radicals in the presence of blue light which can then go on, through the radical pair mechanism, to ulJmately use the Earth’s magneJc field to help the bird navigate. 33

I personally believe that this theory might just be the missing piece of the puzzle as it has not been disproven in any way (yet) but, more research must be done to understand how the bird manages to stabilise the quantum phenomenon of quantum entanglement long enough. The theory may be incomplete due to lack of evidence but is a step in the right direcJon.

Al-Khalili, J. [The Royal InsJtuJon]. (2015, January 30th). Quantum Life: How Physics Can Revolu.onise Biology. [Video File]. 32

Retrieved from <hdps://www.youtube.com/watch?v=wwgQVZju1ZM>.

Thorsten Ritz et al., ‘A Model for Photoreceptor-Based MagnetorecepJon in Birds’, Science Direct <hdp://33

www.sciencedirect.com/science/arJcle/pii/S000634950076629X> [accessed July 10th, 2016].

Page � of 2013

Photosynthesis Photosynthesis is a complicated process and is one of the most important biological processes. It has a near 100% efficiency while our current solar cells are at best, 70% efficient. This also makes 34

photosynthesis a hotspot for quantum biology, as unravelling how photosynthesis gets its efficiency will enable ourselves to create a solar panel with just the same efficiency.

For basic background, photosynthesis is a process by which plants use Carbon-dioxide (from the air through their stoma) and Water (from the ground through their roots) in the presence of light (the light’s energy) and chlorophyll (a green pigment which absorbs light) to produce a hexose sugar and oxygen. EssenJally, this process converts light energy into chemical energy (stored in the sugar) that the plant can uJlise. Photosynthesis occurs solely in a compartment of the cell called the chloroplast.

ParJcularly, the photons are absorbed by the Magnesium atom present in chlorophyll. The outermost electrons of Magnesium are loose and can absorb a photon to become excited and leave the atom. By leaving the atom, the electron creates a vacant hole. The state of an electron when it leaves the atom and is adracted towards the vacant hole is called an exciton. The exciton state lasts for a very short Jme as the electron can very easily radiate out its energy as heat to fit back into its original orbital in the atom.

The goal of the plant is to now transfer this exciton to a part of the chloroplast called the reac8on centre so that the plant may conJnue with the process of photosynthesis. Quantum Biology looks only at this part in parJcular – how the plant goes about transferring the electron fast enough and accurately. Prior models used the idea of ‘random walks’ to explain how the electron is moved to the reacJon centre. In 35

random walks, a parJcle would proceed to its desJnaJon with random moJon, causing the Jme taken to depend on probability. The random walk could not explain how efficient this process is.

However, newer theories suggest that the electron uses ‘quantum walks’ to reach the reacJon centre. 36

In quantum walks, the parJcle walks in many direcJons at the same Jme, allowing it to reach mulJple desJnaJons at once. You can think of this process occurring as the parJcle acJng as a wave and diffracJng.

For any parJcles to quantum walk, the parJcles need to be in a state of quantum coherence and as said before, quantum coherence is thought to dissipate at physiological temperatures due to random parJcle moJon. It is thought that the plant encourages and stabilises a state of quantum coherence to allow the electron transfer rate to be efficient. Evidence for quantum coherence was detected in the Fenna-Mathews-Olson (FMO) complex and other systems in Chlorobaculum tepidum, a green Sulphur bacteria. 37

Jim Al-Khalili and Johnjoe McFadden, Life on the Edge: The Coming Age of Quantum Biology - The Quantum Beat (London: 34

Transworld Publishers, 2014), p. 134.

Kenneth Sauer, ‘Primary Events and the Trapping of Energy’, in ‘Bioenerge.cs of Photosynthesis’, ed. By Date Govindjee 35

(London: Academic Press Inc., 1975), pp.116-175.

Masoud Mohensi et al., ‘Environment-Assisted Quantum Walks in Energy Transfer of PhotosyntheJc Complexes’, Harvard 36

University Center for the Environment <hdp://www.environment.harvard.edu/docs/faculty_pubs/aspuru_walks.pdf> [accessed June 10th, 2016].

Akihito Ishizaki and Graham Fleming, ‘TheoreJcal examinaJon of quantum coherence in a photosyntheJc system at 37

physiological temperature’, Proceedings of the Na.onal Academy of Sciences of the United States of America <hdp://www.pnas.org/content/106/41/17255.full> [accessed July 11th, 2016].

Page � of 2014

These theories sound plausible, that quantum phenomena would be prevalent in all plants even though it was only evidenced from green Sulphur bacteria (and algae ). Bacteria were the first forms of life to 38

photosynthesize on Earth and, chloroplasts were derived from endosymbiosis with these bacteria. SJll, 39

on a scienJfic basis I feel that more experiments should be carried out directly on plant cells to completely prove and convince the public with the presence of quantum phenomena in photosynthesis.

Olfac8on OlfacJon is the sense of smell and, for humans, occurs at the olfactory epithelium in the nose. Discovering the exact mechanism of olfacJon is also a hotspot for research. Finding the exact mechanism allows one to dominate the perfume industry as well as take us a step closer in improving our pesJcides through specific odourants. 40

As expected, the widely accepted theory does not involve any quantum mechanics but, to understand the vibra8on theory of olfacJon, favoured by Quantum Biology, I will first present the steric theory. The widely accepted theory is the Steric Theory or Shape Theory. I believe that the Shape Theory is much more ‘trustworthy’ as it is easy to visualise it in terms of analogies because there is no ‘weird’ quantum physics involved.

The steric theory suggests that sensory neurons on the olfactory epithelium contain receptor sites complementary to the shape of certain ‘scent’ molecules. Hence, adachment of the correct molecules to these receptor sites allows us to smell that molecule. This is essenJally, a lock and key mechanism, 41

with the scent molecules being keys and the appropriate sensory neurons being locks. You can open or acJvate the lock only if you have the correct key (the correct molecule shape). Once the neuron is ‘unlocked’ it will proceed to send impulses to the brain which allows us to smell.

The shape theory can explain why chiral molecules (mirror-imaged molecules) have different scents but 42

cannot explain why similar shaped molecules with just a few differences in structure have completely contrasJng scents or vice versa. An example of chiral molecules that smell different is R-Carvone (Smells like Spearmint) and S-Carvone (smells like Caraway) as seen in Figure 7.

Gregory Scholes et al., ‘DelocalizaJon-Enhanced Long-Range Energy Transfer between Cryptophyte Algae PE545 Antenna 38

Proteins’, ACSPublica.ons <hdp://pubs.acs.org/doi/abs/10.1021/jp108397a> [accessed July 8th, 2016].

Robert Blankenship, ‘Early EvoluJon of Photosynthesis’, Na.onal Center for Biotechnology Informa.on <hdp://39

www.ncbi.nlm.nih.gov/pmc/arJcles/PMC2949000/> [accessed July 9th, 2016].

Michael Rützler, ‘Molecular biology of insect olfacJon: recent progress and conceptual models’, Springer Link <hdp://40

link.springer.com/arJcle/10.1007/s00359-005-0044-y> [accessed July 9th, 2016].

John Amoore, ‘Current Status of the Steric Theory of Odor’, Annals of the New York Academy of Sciences, vol. 116, (July, 41

1964), pp. 457-476.

Jennifer Brookes et al., ‘Odour Character Differences for EnanJomers Correlate with Molecular Flexibility’, Na.onal Center for 42

Biotechnology Informa.on <hdp://www.ncbi.nlm.nih.gov/pmc/arJcles/PMC2610320/#!po=2.63158> [accessed July 8th, 2016].

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�

Figure 7 Source: ExtremeTech <h]p://www.extremetech.com/extreme/146986-olfactory-breakthrough-a-theory-of-quantum-smell>

The other theory (in favour of Quantum Biologists) is the Vibra8on theory of OlfacJon as proposed by Malcolm Dyson and revived by Luca Turin. This theory was one of the first theories (at least, before the 43

Shape Theory) to propose a mechanism for olfacJon. It was regarded controversial as it suggested the involvement of Quantum Tunneling in its mechanism and as there was no major evidence to back it up. The vibraJon theory, in simplicity, suggests that the nose is an IETS spectroscope with the donor 4445

and the recipient molecules being the sensory neuron itself, and the ‘buffer’ molecules being the odorants.

The vibraJon theory is as plausible a theory as any as it meets the basic perquisites that specific buffer molecules (odorants) are required for electron tunneling (odorant detecJon) to occur. Moreover, the vibraJon theory can explain why similarly shaped molecules with minor structural differences have different odours (as those molecules have different bond vibraJons). A piece of evidence towards vibraJon theory is the fact that boranes (compounds of boron and hydrogen) have a sulphurous smell as they possess the same vibraJonal bond frequencies as compounds with hydrogen sulphides. 46

However, the fatal flaw in vibraJon theory is that it cannot explain is how chiral molecules have different scents. IETS cannot disJnguish between chiral molecules, hence, the theory breaks down. Fortunately, 47

another major piece of evidence for the vibraJon theory is that odourants containing heavy isotopes smell different. This was experimented with fruit flies that showed preference to odour with no heavy isotopes and could be trained to do vice versa (however, the point of the experiment is that flies can

John Hewid, ‘New Evidence for the VibraJon Theory of Smell’, PHYS ORG <hdp://phys.org/news/2016-02-evidence-vibraJon-43

theory.html> [accessed July 10th, 2016].

Eric Block et al., ‘Implausibility of the vibraJonal theory of olfacJon’, Na.onal Center for Biotechnology Informa.on <hdp://44

www.ncbi.nlm.nih.gov/pubmed/25901328> [accessed July 10th, 2016].

Leslie Vosshall, ‘Laying a Controversial Smell Theory to Rest’, The Rockfeller University <hdp://vosshall.rockefeller.edu/assets/45

file/PNAS-2015-Vosshall-1507103112.pdf> [accessed July 10th, 2016].

Luca Turin, ‘A Spectroscopic Mechanism for Primary Olfactory RecepJon’, Chemical Senses, vol. 21, (1996), pp.773-791.46

John Hewid, ‘Human Noses: Quantum Smelling Devices’, ExtremeTech <hdp://www.extremetech.com/extreme/146986-47

olfactory-breakthrough-a-theory-of-quantum-smell> [accessed July 11th, 2016].

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differenJate between heavy isotopes and light isotopes). Another study also showed that humans 48

could differenJate between scents of normal and heavier isotopes. However, one may disregard this 49

study as it had a very low sample number.

Unlike the other prior biological processes, OlfacJon is one where, even though IETS may be a plausible mechanism, so is the lock-and-key steric theory. In addiJon, no evidence of electron transfer has been found within these receptors nor such complementary shapes in these receptors. This is simply because not enough research has been done to find the exact structure of these olfactory receptors.

The fight for olfacJon seems like a stalemate but people would sJll tend towards the area where common-sense prevails. Luca Turin plans to produce a definiJve experiment detecJng electron transfer elicited by odorants binding in the receptors, this can prove scepJcs wrong and ulJmately win the duel. 50

Consciousness Incredibly opJmisJc quantum biologists believe that there is a link between consciousness and quantum phenomena.

As menJoned earlier, an electron can either have a clockwise spin or an anJ-clockwise spin. It is said to be in a superposiJon of the two spins unJl it is ‘measured’ by an observer. The ability of humans to break down a superposiJon of states into a single state is the main reason as to why a human’s consciousness is being linked to quantum physics. It was the very act of your free will that determined the superposiJon into a single state, else it would have remained in a superposiJon (The state of a parJcle will enter a superposiJon again once measurement ceases).

I emphasise on the word, ‘human’, as it is believed that humans are the only organisms capable of acJng as an observer (any enJty that can collapse a superposiJon into a single state). Consider, that a cat measures the state of an electron. If the spin is clockwise, the cat is happy. If the spin is anJclockwise, the cat is sad. The cat is in a superposiJon of being happy and sad unJl a human observes it. This usage of ‘human’ can be reduced to YOU. One could now say that, if another human were to view the cat, they would sJll be in a superposiJon unJl ‘you’ collapsed it.

I neglect such studies as they seem too bizarre, even for quantum biology. Although the evidence is not abundant, scienJsts should focus on the simpler aspects of quantum biology first. 51

Philip Ball, ‘Flies sniff out heavy hydrogen’, Nature <hdp://www.nature.com/news/2011/110214/full/news.2011.39.html> 48

[accessed July 10th, 2016].

Simon Gane, ‘Molecular VibraJon-Sensing Component in Human OlfacJon’, PLOS|ONE <hdp://journals.plos.org/plosone/49

arJcle?id=10.1371/journal.pone.0055780> [accessed July 10th, 2016].

Philip Ball, ‘Controversial Theory of Smell Given a Boost’, ChemistryWorld <hdps://www.chemistryworld.com/research/50

controversial-theory-of-smell-given-a-boost/5806.arJcle> [accessed July 10th, 2016].

Ivan London, ‘Quantum Biology and Psychology’, The Journal of General Pyschology, vol. 48, (1952), pp. 123-149: 123.51

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Conclusion I have covered four biological processes that may involve quantum phenomena. Although I have demonstrated the feasibility of quantum models in all these processes, there is sJll a lack of evidence for the scienJfic community to accept such theories.

Looking at photosynthesis, there are 40 to 200 chloroplasts in every plant cell with each chloroplast 52

containing about one billion chlorophyll molecules. With such a vast number of plant cells and an 53

abundance of photons from the sun, it is unnecessary for plants to adapt to adain such efficient quantum walks within them.

Unfortunately, a problem with the experiment involving detecJon of quantum coherence in the green Sulphur bacteria, was that quantum signatures were detected at incredibly low temperatures of 77°K 54

which is far lower from temperatures in plants. ScepJcs could now say that quantum phenomena only occur at such low temperatures in plants, and not at physiological temperature condiJons.

And with OlfacJon, Philip Ball, a scienJst who helped find Quantum Phenomena in Biology, argues that Quantum processes are there not due to selecJon pressures but that organisms are just ‘stuck with it’ – just a side effect. Another scienJst also states, “Tunneling is a fact of life but life has no special effect on tunneling”. Considering that quantum phenomena occur everywhere, it would make sense that life is 55

just ‘stuck with it’ and would resort using classical phenomena instead. Hence, any experiments which set out to find quantum signatures in biological systems would inevitably find it. These detected quantum signatures do not necessarily mean it is involved with, or is used by the organism in such processes.

As shown, many studies claim that quantum processes are prevalent in biological systems, and although I want to believe that biological systems exploit quantum processes, I feel that even if these quantum processes are present they may not purposely be used by the biological system in any beneficial way. But that does not mean we should drop any research on Quantum Biology as conJnuing this research will inevitably contribute to our understanding of biological processes. 56

My conclusion on this EPQ tells me that more studies must be done to fully understand and claim such a controversial fact as all studies show correlaJon and no decisive causaJon. In my opinion, I feel that in the large varieJes of biological processes, there is, at least, one that purposely uses quantum phenomena.

Ki�ma Makgomol and Elizabeth Sheffield, ‘Gametophyte Morphology and Ultrastructure of the Extremely Deep Shade Fern’, 52

Wiley Online Library <hdp://onlinelibrary.wiley.com/doi/10.1046/j.1469-8137.2001.00160.x/full> [accessed July 11th, 2016].

Jerome Wolken, Euglena: An Experimental Organism for Biochemical and Biophysical Studies – Summary (New York: Meredith 53

Publishing Company, 1967), pp.168-201: 171.

Gregory Engel et al., ‘Evidence for Wavelike Energy Transfer Through Quantum Coherence in PhotosyntheJc Systems’, Nature 54

<hdp://www.nature.com/nature/journal/v446/n7137/abs/nature05678.html> [accessed July 9th, 2016].

Ball, P. [The Royal InsJtuJon]. (2015, February 18th). Quantum Biology: An Introduc.on. [Video File]. Retrieved from <hdps://55

www.youtube.com/watch?v=bLeEsYDlXJk>.

Karl Zimmer, ‘The Development of Quantum Biology During the Last Decade’, Acta Radiologica, vol. 46, no. 4, (1956), pp. 56

595-602: 600.

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Page � of 2019

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