Abiogenesis
17 Sep '05 08:262 editsOriginally posted by AThousandYoung[/b]A very interesting post.
Here is what I've written on abiogenesis in the past:
[b]The Earth probably formed about 4.5 billions years ago. It was a hot, inorganic ball of rock with oceans and an atmosphere containing nitrogen, carbon and hydrogen atoms in some gaseous form or another, but no oxygen gas (O2). I don't really know what molecules these atoms were organized in ...[text shortened]... org/wiki/Cell_(biology)#Origins_of_cells[/i]
http://en.wikipedia.org/wiki/Origin_of_life
The Earth probably formed about 4.5 billions years ago. It was a hot, inorganic ball of rock with oceans and an atmosphere containing nitrogen, carbon and hydrogen atoms in some gaseous form or another, but no oxygen gas (O2). I don't really know what molecules these atoms were organized into, but it doesn't really matter. When gasses of made up of these elements are exposed to lightning, ultraviolet light or heat, simple organic molecules will form, as demonstrated by Stanley Miller and Harold Urey in 1953, and I believe others since.
The only 2 major problems I have with the Miller-Urey experiment is: that they require an absence of oxygen as you noted above, as it would oxidise these organic particles and render them useless; the other is that in their experiment they created mounds of destructive tar that would eliminite early life.
Amino acids, short proteins, nucleotides, ATP (and probably other nucleoside triphosphates), and other molecules characteristic of living things are some of the organic molecules that have been observed to form in laboratory recreations of these conditions.
Are these without the problems I cited above?
Now RNA, like DNA, already has an obvious mechanism by which it could replicate itself. This is the point at which substances began to catalyze the synthesis of smaller molecules into copies of themselves; that is, they reproduced. Being genetic material with no proofreading systems with the potential to be exposed to uv light, such RNA chains began to mutate into chains with slightly different base sequences. Any of these which folded into enzymes that catalyzed their own reproduction would begin to out compete the other RNA chains in terms of reproduction and using up the raw materials for reproduction. The process of evolution has begun, even before life existed.
Okay. Although as you said, this is only random chains of nucleotides, not life itself yet. Just like putting a frog (my apologies to FS) in a super-blender, which breaks it down on a microbiological level, would have all the necissary organic material, would this microcosm left to itself, create life? Hense my assertion in calculating the odds.
Now, sometimes more than one molecule of RNA would get trapped inside and begin to self-replicate; sometimes some copies of the RNA inside the protocell would mutate into different forms. In this way different enzymes would come into being, providing a more varied environment inside the protocell.
When I last checked (end 2004) no one had yet synthesized a "protocell" using basic components which has the necessary properties of life (the so-called "bottom-up-approach" ). This is within highly controlled lab environments, compared to the randomness of prebiotic earth. So I'd contend that the protocell theory is just that and hasn't yet been verified scientifically.
This theory sound semi-plausable but there are a couple big jumps in the cell formation that I just can't get to stick. Sure phospholipids spontaniously form the lipid bylayer, and rhybozymes seem to catalyze the cleavage and formation of covalent bonds in RNA strands at specific sites. Where did the mitochondia come from? Or the ATP motors which would provide the gas to run this engine?
Back to Top