23 June 2012

The body electric

cells are powered not by chemical reactions, but by a kind of electricity, specifically by a difference in the concentration of protons (the charged nuclei of hydrogen atoms) across a membrane. Because protons have a positive charge, the concentration difference produces an electrical potential difference between the two sides of the membrane of about 150 millivolts. It might not sound like much, but because it operates over only 5 millionths of a millimetre, the field strength over that tiny distance is enormous, around 30 million volts per metre. That's equivalent to a bolt of lightning.
...this [is] electrical [the] driving force the proton-motive force. It sounds like a term from Star Wars, and that's not inappropriate. Essentially, all cells are powered by a force field as universal to life on Earth as the genetic code. This tremendous electrical potential can be tapped directly, to drive the motion of flagella, for instance, or harnessed to make the energy-rich fuel ATP.
However, the way in which this force field is generated and tapped is extremely complex. The enzyme that makes ATP is a rotating motor powered by the inward flow of protons. Another protein that helps to generate the membrane potential, NADH dehydrogenase, is like a steam engine, with a moving piston for pumping out protons.
-- from Life: is it inevitable or just a fluke? in which Nick Lane once again champions the hypothesis that the proton gradient at deep sea alkaline vents drove the origin of life on Earth.  'Far from being some mysterious exception to the second law of thermodynamics...life is in fact driven by it.'

Lane argues that similar circumstances would necessarily hold on other planets, but that the jump to eukaryotic cells is likely to be vastly rarer.

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