Origin of life: warm pond encapsolated theory (Introduction)

by David Turell , Saturday, March 19, 2016, 00:43 (2960 days ago) @ David Turell

An optimistic idea involving encapsulation with a lipid envelop in warm ponds: - "For the past 40 years, David Deamer has been obsessed with membranes. Specifically, he is fascinated by cell membranes, the fatty envelopes that encase our cells. They may seem unremarkable, but Deamer, a biochemist at the University of California, Santa Cruz, is convinced that membranes like these sparked the emergence of life. As he envisions it, they corralled the chemicals of the early Earth, serving as an incubator for the reactions that created the first biological molecules. - "One of the great initial challenges in the emergence of life was for simple, common molecules to develop greater complexity. This process resulted, most notably, in the appearance of RNA, long theorized to have been the first biological molecule. RNA is a polymer — a chemical chain made up of repeating subunits — that has proved extremely difficult to make under conditions similar to those on the early Earth. - *** - "Deamer thinks that volcanic landmasses similar to those in Iceland today would have made a hospitable birthplace for his proto-cells. Freshwater pools scattered across steamy hydrothermal fields would be subject to regular rounds of heating and cooling. That cycle could have concentrated the necessary ingredients — including both lipids and the building blocks for RNA — and provided the energy needed to stitch those building blocks into biological polymers. Deamer is now trying to re-create these conditions in the lab. His goal is to synthesize RNA and DNA polymers. - *** - "Life resists a simple abstract definition. When I try to define life, I put together a set of a dozen properties that don't fit anything not alive. A few of them are simple: reproduction, evolution, and metabolism. - *** - "DNA is the center of all life, but it can't be considered alive even though it has all the information required to make a living thing. DNA cannot reproduce by itself. Put DNA in a test tube with water, and it just slowly breaks into different pieces. So right away, you see the limitation of thinking about single molecules as being alive. - "To get a bit of what we call growth, you have to add the subunits of DNA, an enzyme to replicate the DNA, and energy to power the reaction. Now we have molecules that can reproduce themselves if they have certain ingredients. Are they alive yet? The answer is still no, because sooner or later the subunits are used up and reproduction comes to a screeching halt. So how do we get to a system that's really alive? That's what we and others are trying to do. The only way we can think of is to put DNA into a membranous compartment. - *** - "Organic compounds accumulated in the pools, washed there by precipitation that rained down on the volcanic landmasses. The pools went through wetting and drying cycles, forming a concentrated film of organic compounds on the rocks like the ring in a bathtub. Within that film, interesting things can happen. Lipids can self-assemble into membrane-like structures, and the subunits of RNA or other polymers join together to create long chains. - *** - "To get the thing to replicate would be a big deal. To do that, we need a ribozyme that makes our polymerization reaction go faster. But we have a long way to go before we can find that kind of ribozyme. - "We'll probably be able to make lab life, but I'm not sure we can claim that's how life began. The life we're trying to synthesize is going to be a very technical life, based in a lab with clean reagents and so forth. I'm not sure we can call that the origin of life until it becomes a self-growing system, until we put that system in an outside environment and watch it grow. - "Although we will never know with certainty how life did begin, it seems eminently possible that we will understand how life can begin on any habitable planet." - Comment: Supreme optimism, and where will all those organic compounds come from? Meteorites have delivered only 8 of the 20 needed amino acids.