Molecules in exact synchrony maintain a coherence that is usually lost in the molecular bustle of a normal temperature cell. The timing of the synchrony must be almost perfect to produce this quantum effect, so how do photosynthetic bacteria manage it?
One theory is that cell microtubule structures orchestrate it (Penrose & Hameroff, 2017). Microtubules are self-assembling polymers that appeared over a billion years ago and form the skeleton of all cells today, to affect shape, growth and function. Given that coherence plays a role in enzyme activity (Frohlich, 1970), the helical paths of microtubules evolved synchronous oscillations to allow strong Frohlich coherence at room temperatures (Samsonovich et al., 1992).
If the cell structure oscillates synchronously, the receptor molecules in it will do the same, allowing them to superpose, cohere and act as one. That cell structure can raise quantum effects from atomic to cell timescales has led to the study of quantum effects in other biological puzzles, like smell, protein folding, ion channels and bird navigation (Gauger, 2011).
Orchestrated coherence theory argues that brain microtubules don’t just unify cells but also us, making the brain a quantum computer that processes information in a way classical processing can’t (Penrose & Hameroff, 2017). Critics note that while microtubules enable coherence at cell timescales, human consciousness requires a time scale many orders of magnitude above that (Jedlicka, 2017). Also, microtubules can’t explain why some brain events are conscious and others aren’t (Baars & Edelmann, 2012). Comatose brains have as many microtubules as normal ones so why aren’t they conscious? About half the human brain doesn’t support consciousness directly but nerves in these regions contain just as many microtubules.
Penrose and Hameroff make the case for consciousness at the cell scale based on a tubulin decoherence time of 10-13 seconds (Tegmark, 2000) but even their 10-6 seconds best estimate is too brief for human consciousness (Penrose & Hameroff, 2017) p27. Tubulin-based entanglement may enable cell-scale consciousness but more is needed for brain scale consciousness.