Big Jase said:
hey ...
i have a mate and he is always talking about this Primidial Soup.. "alphabetty spergetti" he calls it..where the begining was formed... i just want some more insite into this theory so i can make me own mind up...
cheers
napajohn said:
\Besides we know that all precambrian rock suggests oxidation meaning the presence of oxygen...but they won't tell you that in your biology class..makes the Miller experiment kinda look stupid.
No, only you look stupid here because you don't seem to know anything about evolution which does not address how life began on this planet. However, abiogenesis does and there is quite a lot of evidence to support it. Because Big Jase asked about abiogenesis, here's what's the progress of abiogenesis in trying to model conditions on a pre-biotic Earth that would lead to life as we know it in 3 parts............
PART 1--Overview of Abiogenesis
Here is what abiogenesis or spontaneous creation (it was an "RNA world") is all about in this animated lecture series from the School of Chemistry, University of Oxford, England: {You will need plug-ins for viewing animations and molecules..... can get by without it, but that's up to the reader}
Abiogenesis/The Prebiotic World and the Evidence(Oparin/Haldane Hypothesis)
The RNA-World/Oparin-Haldane Hypothesis
RNA is the only known macromolecule that can both encode genetic information and also act as a biocatalyst. RNA molecules that perform enzymatic functions (biocatalysts) are called ribozymes.
One of the most interesting of these ribozymes was discovered by Tom Cech when he discoved a self-splicing RNA in the single celled organism Tetrahymena thermophila. This RNA splice out it's own introns WITHOUT the assistance of proteins.
A demonstration of Cech's ribozyme go to this WEBSITE and click on the links under the subsection entitled Group I Intron Splicing
HERE (pdf file) is Cech's lecture to the Nobel Laureate Committees on this discovery (Nobel Prize for chemistry 1989)that gives both a diagram of the splicing and his original research.
The observation of the above forms
the basis for the 'RNA world' model which suggests that both the genetic and enzymatic components of early cells were RNA molecules. There are
some problems with the "RNA-world":
- Making the sugar ribose under prebiotic conditions is problematic (it is unstable, in equilibrium with other anomeric forms, etc.) .
- Prebiotic conditions make it difficult to make nucleosides
- The phosphate chemistry utilized to activate RNA nucleotides in present-day living systems is not viewed as feasible under the primitive conditions of the pre-biotic world. However, nucleotide activation can also be based on imidazole chemistry, so this is not an insoluble problem.
- The 4 bases have to be joined to the sugar ribose, which under natural conditions is unstable. As of now, the only techniques discovered for joining the bases to ribose result in low yields, something unsuitable for the RNA world scenario.
- Polymerization of the nucleotides into RNA would have been a problem (assembling them so that they actually contained "information").
- The temperature of a primitive Earth would have made it difficult for RNA (once assembled) to remain stable.
Does this mean "curtains" for the RNA world scenario? NO. RNA could have "evolved" from other molecules better able to have withstood the harsh conditions of the prebiotic world. Here are a couple of articles on likely candidates for the "Pre-RNA world".......
1. Leslie Orgel--PNAs as Precursors to an RNA World Orgel and his group at the Salk Institute, studied a compound known as peptide nucleic acid (PNA). PNA has the ability to replicate itself and catalyze reactions but is much simpler than RNA. Orgel et al. demonstrated that PNA can act as a template both for its own replication and for the formation of RNA from its subcomponents. (Orgel, Leslie E.
The Origin of Life on the Earth p 77-83 Scientific American, October 1994.)
2. A TNA World? (Synthesis of a chemical relative of RNA as a Possible Candidate for the First Self-Assembling, Self-Replicating Molecules)
IMO, the following quote from
Quetzal, on the Self-replicating molecules thread from the EvC forum summed up the situation as it stands for the "Pre-RNA World.......
[...]both pyranosyl-RNA and PNA replicators are mutable - beyond a certain point you can add/remove base pairs as much as you want without effecting the self-replicating capability (I think Schleigman went from 4500 bp to 220 bp pRNA over 70 generations or so and still had a replicator). Meaning you can have new features added to the original chain, and hence variation, and ultimately evolution by natural selection. Once you've set up the nucleic acid replicators, coopting amino acids and catalysing their production, glomming on to lipids, etc is just chemistry.
Now actually getting to pRNA or PNA outside a lab is a bit more chancy. Both require pretty stringent conditions.
**===>NOTE: This is the "gap" where creationist/IDist God-of-Gaps currently resides............... Of course, if you let things go their way in a real, aqueous "soup", the necessary chemistry is hard to come by (a fact mentioned in the above). However, if you isolate the chemical environment in protected bubbles, this does not happen.
Life out of magma: a new theory for the origin of life, by Lucido, G.Nuovo Cimento Della Societa Italiana di Fisica D - Condensed matter, Atomic, Molecular and Chemical Physics, Fluids, Plasmas, Biophysics 20(12): 2575-2591; December, 1998
ABSTRACT
On the basis of colloid physical chemistry and taking into account the foundations of the thermodynamics of the unsteady state, a new theory of the origin of life is proposed. The temperature prevailing on the early Earth was too high for any form of life to be formed. The basic elements were distributed chaotically in space and constituted the hot primordial magma ocean. On cooling, however, a certain order slowly but surely began to establish itself. In particular a surficial colloidal soup originated in this magma ocean, once phase separation phenomena started. Subsequently in the long run, at or near the Earth's surface, amphiphilic molecules contained in this colloidal soup began to distribute themselves in vesicular aggregates. Every vesicle structure was surrounded by a barrier that kept it separate from other vesicle structures and from the environment. From a thermodynamic stand point there was a three-phase system: interior, barrier and exterior. The formation of these structures was the crucial event for the origin of cellular life. As to the origin of the earliest cell, the following sequence of events is proposed: primitive hot magma --> spinodal decomposition --> nucleation and growth --> colloidal soup --> amphiphilic molecules --> spontaneous vesicles --> functioning protocells --> prokaryotic cell.
For the ability of abiogenic
proteinoids to self-organize into protocells the reference by Sidney W. Fox:
The evolutionary significance of phase-separated microsystems. Orig Life. 1976 Jan;7(1):49-68. For more on the potential of Fox's proteinoid microspheres go to my previous post to Ikester'
Of course, this idea requires "vesicular aggregates". But you can form vesicles on rock surfaces, which then enter the "soup"
Origin of life. II. From prebiotic replicators to protocells, by Turian, G.Archives des Sciences 52(2): 101-109; August, 1999
ABSTRACT
Primitive microvesicles (coacervates, microspheres, marigranules, etc.), free-born in aqueous media, are only protometabolic proteinoids surrounded by an amphiphilic protomembrane. In contrast, surface-born microvesicles could be initiated in the pores of watered rocks providing primary boundaries coated by amphiphilic compounds and acting as sinks for primitive peptides and their coding nucleobases N-P anchored on polyphosphates. Only presumed replication of these prenucleic infopolymers would qualify the basipetally budded microvesicles as protocells.
But can you get interesting chemistry in the microvesicles?
Production of RNA by a Polymerase Protein Encapsulated within Phospholipid-Vesicles, by Chakrabarti, A.C., Breaker, R.R., Joyce, G.F., Deamer, D.W.Journal of Molecular Evolution 39(6): 555-559; 1994
ABSTRACT
Catalyzed polymerization reactions represent a primary anabolic activity of all cells. It can be assumed that early cells carried out such reactions, in which macromolecular catalysts were encapsulated within some type of boundary membrane. In the experiments described here, we show that a template independent RNA polymerase (polynucleotide phosphorylase) can be encapsulated in dimyristoyl phosphatidylcholine vesicles without substrate. When the substrate adenosine diphosphate (ADP) was provided externally, long-chain RNA polymers were synthesized within the vesicles. Substrate flux was maximized by maintaining the vesicles at the phase transition temperature of the component lipid. A protease was introduced externally as an additional control. Free enzyme was inactivated under identical conditions. RNA products were visualized in situ by ethidium bromide fluorescence. The products were harvested from the liposomes, radiolabeled, and analyzed by polyacrylamide gel electrophoresis. Encapsulated catalysts represent a model for primitive cellular systems in which an RNA polymerase was entrapped within a protected microenvironment.
