14 April 2007

Quantum Photosynthesis

According to Physorg (arrived via Slashdot), our understanding of photosynthesis has been wrong all the while. According to a paper published days ago in the esteemed Nature journal, the photosynthesis process actually involves quantum coherence.

From the Physorg article,

"We have obtained the first direct evidence that remarkably long-lived wavelike electronic quantum coherence plays an important part in energy transfer processes during photosynthesis," said Graham Fleming, the principal investigator for the study. “This wavelike characteristic can explain the extreme efficiency of the energy transfer because it enables the system to simultaneously sample all the potential energy pathways and choose the most efficient one.”

They aren't the ones to first propose the idea, but they provided the first direct evidence of it.

Said [Greg] Engel, "[...] While the possibility that photosynthetic energy transfer might involve quantum oscillations was first suggested more than 70 years ago, the wavelike motion of excitation energy had never been observed until now."

As I understand it, it appears that there is coherence between the donor and acceptor molecules due to impinging photons, resulting in very rapid energy transfer. However, this is not my area; I believe this belongs to either the realm of biophysics or quantum chemistry. Nonetheless, from a physics perspective it is very interesting to see quantum mechanical processes manifesting all around us.

If this is indeed the case and the underlying theory can be worked out, it will be critical in our knowledge to build highly efficient solar cells. But this also means that the simple chemical interpretation of photosynthesis has to be thrown out of the window, as thus from secondary school or JC textbooks. Ah well, at least next time there's a need to cut the syllabus, it will be clear which one will go.

And as a last thought, if photosynthesis is a quantum mechanical process, then does that means that the leaf has both photosynthesized and not photosynthesized?

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