Células vivas são 'computadores químicos'

terça-feira, junho 30, 2009

Review: Wetware by Dennis Bray

30 June 2009 by Graham Lawton

Book information
Wetware by Dennis Bray
Published by: Yale University Press
Price: £18.99/$28

A BAG of biochemistry less than a millimetre across that spends most of its life attached to pond scum, the single-celled organism Stentor roeselii doesn't sound impressive. Yet its behaviour is remarkably sophisticated. Squirt a jet of water at a Stentor and it will dive into its mucus holdfast, emerging cautiously soon after. But squirt another identical jet at the same Stentor and it ignores it.


These single-celled protozoa, Stentor roeselii, are actually complex chemical computers (Image: Volker Steger / Christian Barpelle / SPL)

How can such complex behaviour arise in such a simple life form? This is the question that Dennis Bray tackles with remarkable clarity and style in this excellent book. In a nutshell, his answer is that living cells, like the single-celled protozoa pictured, are chemical computers. They take information from the environment and process it to produce behavioural "outputs". The processing units are proteins, which perform all the same operations as the logic gates of a computer. Inputs from the environment cause the proteins to flip shape, to aggregate, and to chemically modify other proteins in a cascade of information processing that sweeps through the cell until it reaches effector proteins that make the cell move or change shape.


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