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What is the difference between a normal molecule and a replicating molecule like RNA or DNA ?
What mechanism triggers a non replicating molecule to suddenly start replicating itself ?
Also, when RNA starting replicating, did it already have the instructions to build a cell around itself to keep it safe or was it floating around on its own without any protection ?
Just musing really, but cheers for any answers
Far away is close at hand in images of elsewhere...
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In organic chemistry, molecular size and complexity.Originally Posted by kevin1981
Very large and complex molecules such as RNA/DNA are self-replicators.
Autocatalysis is hypothesized as possibly being a possible phase in the lead-up to organic molecular self replication:
So-called 'clock reactions' such as the Belousov–Zhabotinsky reaction are one such example of autocatalysis. (Others are also known as existing).
The evolution of cell membranes is the subject of yet other hypotheses. In general lipid formation has been demonstrated (in lab environments) as leading towards fundamental membrane-like functionality.
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There are much simpler replicators.
They're not really useful as a base for transcription, since they're super simple.
It's not a self-replicating molecule, it's a cycle of molecules whose outcome is a second copy of the first molecule.
I wish I could remember what it's called.
It's got something to do with Chlorine and occurs near hydrothermal vents, where the right elements are available.
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In the context of discussions about modern biological mechanisms and processes, 'self-replication' is fairly well explained.
In the context of so-called 'pre-biotic' chemistries however, I think the terms 'replication' and more specifically, 'self-replication', really take on a different meaning.
I'd be interested to see references/papers on this(?)
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I'm not exactly sure what you mean by a "replicating molecule." A molecule that is created by some program? In that case, I think that all proteins are replicating molecules. Or do you mean one that has a code in it that is used to make other molecules?
As above, so below
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He mentioned RNA and DNA. Surely he literally means self-replicating.
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But they're not self-replicating as far as I know. A molecule of RNA or DNA left in a solution will not replicate.
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Yes, and a good introduction to something like 20 years of study on the question is At Home in the Universe by Stuart Kauffman.
Everyone is entitled to his own opinion, but not his own facts.
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The so-called 'translational apparatus', (ribosomes and other proteins), are themselves derived from subunits of the RNA molecule (rRNA).
In this sense, RNA is still referred to as self-replicating (tis 'the origin').
How functional ribsosomes came about in the first place, is one of the big questions, though.
They have been artificially synthesised (by Ventner etc) but this was done based on the known structures of modern fully functional ribosomes.
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Yep .. even though he cast a big opinion in his conclusions about the 'inevitability' of it all.
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Interestingly, it seems that researchers have only just recently succceded in engineering a ribosome to replicate itself for the very first time:Previously, they've only been able to get ribosomes to replicate straight strands of RNA, thus blocking its ability to copy its (very) folded self.Normally when copying RNA, an enzyme would add single bases (C, G, A or U) one at a time, but the new ribozyme uses three bases joined together, as a 'triplet' (e.g. GAU). These triplet building blocks enable the ribozyme to copy folded RNA, because the triplets bind to the RNA much more strongly and cause it to unravel—so the new ribozyme can copy its own folded RNA strands.
Also interesting, (from the same article), is that triplet binding seems to also be a 'sweet spot' for opening up the folds, whilst maintaining a high replication accuracy.
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I would argue they are self-replicating in that they are able to replicate themselves.
What you're describing sounds to me more like spontaneous replication. i.e. that they would replicate if simply left to their own devices. They won't of course, but I don't think that's what the OP is looking for anyway.
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I know it’s a subtle point, but I was thinking that it is the cell that is self-replicating, and that the genome provides the code that guides the process.
Sent from my iPhone using Tapatalk
As above, so below
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Ah! Found it again! Not chlorine - citric acid!!
https://en.wikipedia.org/wiki/Citric_acid_cycle
It's a cyclic reaction that, provided the right elements, produces more citric acid, which can then be used to start another cycle.
Again, it's too simple a molecule to encode anything useful, but it's a start. Give it a billion years or so...
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There are other so-called 'self-replicators' also.
It has been demonstrated that amyloid structures (in a 'soup') can spontaneously form from simple amino acids which settle at just the right sites, and then chemically combine with eachother. Amyloids are composed of short peptides and form fibres which are also able to accelerate chemical reactions (same as enzymes). This peptide synthesis mechanism, when applied to the amyloids themselves, gives rise to the 'self-replication' argument.
The researchers campaigning for this one, argue that the formation and replication mechanism is more 'plausible' (to them) than the 'RNA-first' hypothesis of abiogenesis.
Paper here.
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Yep .. thanks.
A key part of metabolism .. which makes available the energy for cellular processes, (including self-replication).
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