This document discusses the potential role of quantum effects in biological processes like photosynthesis, olfaction, bird navigation, and consciousness. It describes how resonant energy transfer during photosynthesis may involve quantum superposition and coherence to efficiently transport excitation energy. For olfaction, it suggests that electron tunneling enabled by molecular vibrations could explain how different molecules with varying shapes but similar vibrations can smell alike. Regarding bird navigation, it proposes that cryptochrome proteins may experience quantum entanglement to detect magnetic fields. Finally, it presents the idea that consciousness could arise from quantum vibrations in microtubules orchestrated by synaptic inputs in the brain.

1. Quantum Biology
Francesca Davis
Physics 112, Spring 2014

2. Topics
• Photosynthesis and Superposition
• Olfaction and ElectronTunneling
• Navigation in birds and Entanglement
• Consciousness may arise from quantum
vibrations in microtubules

3. Photosynthesis occurs
in
Chloroplast’s
Thylakoid Membrane

4. Resonant EnergyTransfer uses coherent
superposition for increased efficiency

5. Resonant EnergyTransfer
• 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?

6. Resonant EnergyTransfer
• 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…

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

8. ElectronTunneling
• 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.

9. 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: http://phys.org/news89542035.html#jCp

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

11. Quantum Entanglement
• “Spooky action at a distance”
• Glove analogy
• Collapse of wave function when measured
• Measurement terminates the evolution of delocalized objects

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.

14. Sources
• Gane et al. (2013) MolecularVibration-Sensing Component of Human Olfaction. PLoS ONE.
• Maliszweski, P. Several Failed Attempts to Explain Quantum Entanglement. McSweeney’s
http://www.mcsweeneys.net/
• Palmer, J. (2013) ‘Quantum smell’ IdeaGains Ground. BBC News,
http://www.bbc.com/news/science-environment-21150046
• Pratt, C. , Cornely, K. (2014) Essential Biochemistry 3rd. Ed.,Wiley.
• http://www.universetoday.com/109525/quantum-entanglement-explained/
• QuantumTunnelling http://en.wikipedia.org/wiki/Quantum_tunnelling, Accessed May 3rd, 2014.
• Quantum Entanglement,
http://en.wikipedia.org/wiki/Quantum_entanglement#Methods_of_creating_entanglement ,
Accessed May 3rd, 2014.