4 December 2014

All possible paths simultaneously

Below you lies just one of the trillions of photosynthetic machines that manufacture the world's biomass [some 16,000 tonnes every second]. From your vantage point you can see that...although there are plenty of billiard-ball like turbulent molecular collisions going on, there is also an impressive degree of order. The membranous surfaces of the thylakoid is studded with craggy green islands forested with tree-like structures terminating in antennae-like pentagonal plates. These...are light harvesting molecules call chromophores, of which chlorophyl is the most famous example.
from Life on the Edge: the Coming Age of Quantum Biology by Jim Al-Khalili and Johnjoe McFadden (2014)
The very best photovoltaic cells...convert sunlight to electrical energy with an efficiency of around 35%; for more affordable cells the figure is closer to 20%. Plants accomplish the same process with about 90% efficiency during the first stage of photosynthesis. 
Efficiently converting light into electricity requires preserving the energy of an exciton [an electron-ion pair] as it travels deep within reaction centre of the leaf [and] the key to [this] lies in way it travels to the reaction centre. Researchers discovered to their great surprise in 2007 that plants use a [trick] from the realm of quantum physics to help excitons find their way. Rather than bumping randomly through a forest of chlorophyll molecules until they happen to reach their destination...each exciton spreads out over all possible paths simultaneously, and then funnels down through the most efficient route.
from How plants exploit sunlight so efficiently, The Economist.

Image from synechocystis.asu.edu

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