1. Francesca Davis Physics 112, Spring 2014
Quantum Biology
Francesca Davis
Physics 112, Spring 2014
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2. Topics Photosynthesis and Superposition
Olfaction and Electron Tunneling
Navigation in birds and Entanglement
Consciousness may arise from quantum vibrations in microtubules

3. Photosynthesis occurs in Chloroplast’s Thylakoid Membrane
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Showing antenna pigments, light harvesting complexes etc. Stroma, Lumen… Chromophore is moiety in a pigment molecule that absorbs light giving pigment it’s characteristic color.

4. Resonant Energy Transfer uses coherent superposition for increased efficiency
Exciton transfer aka resonance energy transfer: “precisely aligned pigment molecules transfer energy to chlorophyll in the reaction center.” Essential Biochemistry 3rd Ed.
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5. Resonant Energy Transfer
Previously assumed that excitons incoherently jumped around between chromophores but…
Quantum effects better explain efficient light harvesting (50% to 90%)
Potential for improving solar cells or photosynthetic computing?
Exciton = electron + electron hole
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6. Resonant Energy Transfer
Delocalized excitation across several chromophores
Electronic coherence among chromophores (quantum superposition of the electronically excited states of different molecules)
Allows photon to find most efficient path
Some decoherence needed to ensure that energy doesn’t flow the wrong way -Do let the door hit you on your way in…
Exciton = electron + electron hole
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7. Quantum Effects and Olfaction
Shape theory of smell -Shapes of odorant and receptor must fit together to transduce signal.
Problems with this theory:
Molecules with same shape but different vibrations typically have different smells
Molecules with different shapes but similar vibrational spectra smell similar
Luca Turin’s theory. Tested with normal and deuterated molecules. Drosophila can tell difference in Acetophenone. Also Fish. Humans tested with musk odorants that were normal and deuterated. Found a difference in smell. While a wide variety of molecular shapes for wildtype musk molecules all are variations on same type of smell. Secondary descriptors of Animalic, sweet oily, etc., Deuterated versions all less musky and more “burnt, roasted, nutty.” Vibration in C-H bonds (stretch, wag, scissor) hypothesized to be important to smell. Deuteration alters this vibration. “…Vibrational spectra a better predictor of odor character than shape discriptors.” Gane et al. (2013) Molecular Vibration-Sensing Component in Human Olfaction.
Carvone enatiomers: speamint and caraway
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8. Electron Tunneling
In Classical Mechanics, electron would need enough energy to get through the barrier (molecules)
In Quantum mechanics, the particle can “borrow” energy from molecules around it
Vibrations of particle and barrier are coherent.
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9. G coupled protein receptor
G coupled protein receptor. Should have 7 transmembrane domains but they only show five. Draw membrane and also G protein coupled to intracellular domain.
The process of smell via electron tunneling: (a), an electron in the nasal receptor finds its way to the donor component of the receptor; (b) and (c), a scent molecule’s vibrational frequency enables the electron to tunnel to a different energy state; (d) electron travels to the acceptor unit and molecule leaves. Credit: Marshall Stoneham, et al. Read more at: 

10. Navigation in Birds
Cryptochrome protein in Birds’ eyes have pairs of electrons quantumly entangled
If one electron moves over a few nanometers it will experience Earth’s magnetic field differently
Triggers chemical reactions in optical cells and ultimately behavioral pathways
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11. Quantum Entanglement “Spooky action at a distance” Glove analogy
Collapse of wave function when measured
Measurement terminates the evolution of delocalized objects
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E.g.
Photons entangled with regards to polarization. Nonlinear crystal splits a photon into two entangled photons. Total E and momenta conserved.
Subatomic particle decays into two particles.
Electrons can be confined with quantum dots to become entangled. “Excitation and emission of quantum dots highly tunable.” confines excitons in three dimensions.

12. Consciousness Orchestrated Objective Reduction
Controversial theory –Brain is “too wet, warm and noisy”
Consciousness due to quantum vibrations in microtubules
Cytoskeletal element important to cellular structure and transport
Synaptic inputs “orchestrate” quantum vibrations in microtubules.
Penrose
Synaptic input orchestrates consciousness. Other research suggests Anesthesia may act on microtubules. EEG waves may result from microtubule quantum vibrations.
Objective Reduction seems to correspond to wave collapse????
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13. Images: http://jonlieffmd
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14. Sources
Gane et al. (2013) Molecular Vibration-Sensing Component of Human Olfaction. PLoS ONE.
Maliszweski, P. Several Failed Attempts to Explain Quantum Entanglement. McSweeney’s
Palmer, J. (2013) ‘Quantum smell’ Idea Gains Ground. BBC News,
Pratt, C. , Cornely, K. (2014) Essential Biochemistry 3rd. Ed., Wiley.
Quantum Tunnelling Accessed May 3rd, 2014.
Quantum Entanglement, , Accessed May 3rd, 2014.