Theoretical origin of life: energy at thermal vents (Introduction)

by David Turell , Monday, January 11, 2016, 19:13 (3239 days ago) @ David Turell

There are many mineral and much energy at thermal vents. The article assumes life might have started there:-https://aeon.co/essays/why-life-is-not-a-thing-but-a-restless-manner-of-being?utm_source=Aeon+Newsletter&utm_campaign=7d4d0e0730-Daily_newsletter_Monday_11th_Jan1_11_2016&utm_medium=email&utm_term=0_411a82e59d-7d4d0e0730-68942561-"But within modern organisms there is another clue to life's origins, one that is more obscure than DNA but just as universal - the way cells harvest energy by shuffling around electrically charged molecules. This process goes by the mouthful ‘chemiosmosis', and was first proposed in 1961 by the eccentric British biochemist Peter Mitchell. Chemiosmosis lacks the coded rigour of DNA, but that primal messiness might be exactly what makes it so revealing.-"Energy, Russell thinks, must have preceded anything resembling DNA or RNA, so the origin of chemiosmosis could help to reveal how the first organisms arose. Chemiosmosis takes place deep in our body's cells, most of which harbour hundreds or thousands of microscopic structures called mitochondria. The mitochondria extract the chemical energy from food and, with the help of the oxygen we breathe, convert it into a molecule called adenosine triphosphate (ATP). Just as much as DNA, ATP is the molecule of life; it is the currency we spend to grow, move or think. Every second, each of our body's 40 trillion cells use around 10 million molecules of ATP. We can turn over our entire body weight in this special substance every day.-"The flow of energy across the membranes of the mitochondria occurs through a molecular Rube Goldberg contraption so elaborate it almost defies comprehension. A chain of dozens of proteins, each consisting of thousands of atoms, traps high-energy electrons (derived from food), and passes them down the chain like a bucket brigade. The movement of electrons through the proteins in the chain creates an electrical current, which is used to trap massive numbers of protons between the mitochondrion's inner and outer membranes. The only escape for the protons is through another remarkable protein called ATP synthase. It is an engineering miracle, a nanomachine complete with a molecular rotor, stator and driveshaft, which, as protons fall through it, spins like a waterwheel - hundreds of times per second - to produce ATP.-***-"In a series of papers dating back to 2003, Russell and Martin teamed up to explore the biological implications of the chemical-garden scenario. In their fleshed-out version of the hypothesis, life began not as a free-roaming creature, feeding off natural organic molecules drifting in the ocean, but as a tenant that made its own food in the mineral compartments of underwater rocks. At first, ocean vents were simply sites of geology, gases and dissolved minerals bubbling up to form rocks. But in the microcompartments of those rocks, something unusual began to happen. The carbon dioxide in the ocean reacted with the hydrogen from the vents. Under typical conditions, this reaction wouldn't occur, but the minerals in the compartment walls, rich in iron and sulfur, coaxed this reluctant partnership. These reactions created small organic molecules such as acetyl-CoA, one of the most ancient metabolic pathways ever discovered.-***-"Biological information systems - the codes needed for life to reproduce - cannot just spring into existence.-***-"In this view, life's origin isn't an origin at all, but just another step in a sequence of events set in motion by the Big Bang.-"Thinking of life in terms of energy challenges the very definition of life. ‘It's not what life is,' Russell said. ‘It's what life does.' After all, you replace each atom in your body, on average, every few years. In that sense, life isn't a thing so much as a manner of being, a restless fit of destruction and creation. If it can be defined at all, it is this: life is a self-sustaining, highly organised flux, a natural way that matter and energy express themselves under certain conditions. "-Comment: Note the bolds I made. Mitochondria are very complex. Acetyl CoA is a small enzyme but a very complex molecule. Articles are always hopeful.