Watchful eyes, thoughtful mind

Earth and us ….. past, present and future ….. connected?

Here we go again … December 3, 2009

Filed under: biology,chemistry,geology,oceanography,unconventional — Radiance @ 10:00 AM

03_32_ATP_and_ADP_cycleTechnological advances have a peculiar way about them. They always seem to progress in steps of exponential growth followed by a period of lull. This trend is closely followed by our ability to learn new things about the world around us. And so human beings, particularly scientists, go through alternating periods of “discovery frenzy” and complacency that there’s nothing more left to explain. We had hit such a complacent period a few decades ago as regards origin and evolution of life on our planet. But now we’re in the “discovery frenzy” stage for the same and hence getting disillusioned about many theories and principles that we thought were invincible. Many new discoveries using newest and (so far) most accurate techniques are making it more than clear that the question of “how life originated on Earth?” is far from settled.

Nick Lane, the first Provost’s Venture Research Fellow at University College London and author of Life Ascending: The ten great inventions of evolution, has written a detailed article in the New Scientist on 19th October, 2009 about an alternative theory for origin of life. This is only the latest one in the long line of many such that came before it but didn’t survive the scientific scrutiny. It is based on not-so-conventional ideas of Peter Mitchell who was initially dismissed by his contemporaries but won a Nobel in 1978. Geochemist Mike Russell of NASA’s Jet Propulsion Laboratory in Pasadena, California is rethinking the origin of life and finds Mitchell’s ‘Chemiosmosis’ a valid candidate. The following text from Lane’s article explains the idea,

Before Mitchell, everyone assumed that cells got their energy using straightforward chemistry. The universal energy currency of life is a molecule called ATP […] generated from food by a series of standard chemical reactions. Mitchell thought otherwise. Life, he argued, is powered not by the kind of chemistry that goes on in a test tube but by a kind of electricity. The energy from food, […] is used to pump […] protons, through a membrane. As protons accumulate on one side, an electrochemical gradient builds up across the membrane. Given the chance, the protons will flow back across, releasing energy that can be harnessed to assemble ATP molecules. In energy terms, the process is analogous to filling a raised tank with buckets of water, then using the water to drive a waterwheel.

lst cityEven though this seems a counterintuitive and roundabout way to produce energy to power life, there is a growing body of evidence of this process occurring everywhere in nature. Aided with the latest knowledge of fellow biologists and using a logical process of elimination, author Lane reaches a baffling conclusion. The common ancestor of all life on Earth was something with components of a modern cell but no walls or boundaries. Now that’s a stunner! But nature has never failed to provide us evidence for the most unexpected and hence broaden the horizons of our knowledge. So along came the surprise discovery of alkaline hyrdrothermal vents just off the mid-Atlantic ridge in 2000. It turns out that the combination of their peculiar structure and the chemical conditions of atmosphere and ocean the on the early Earth provide a perfect toolkit for the production of DNA, RNA, an ATP prototype, all without the requirement for a wall or boundary. I have only given an outline of what Nick Lane’s article describes in a great detail. So if my summary makes you curious, go read the full article.

I’ll end this post with the apt ending Nick Lane provides to his article,

Many details have yet to be filled in, and it may never be possible to prove beyond any doubt that life evolved by this mechanism. The evidence, however, is growing. This scenario matches the known properties of all life on Earth, is energetically plausible – and returns Mitchell’s great theory to its rightful place at the very centre of biology.

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