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Self-Replicating Molecules.
How did certain chemicals combine to produce the first self-replicating molecules?
Answers
We don't know. Writings on the subject are still full of the words 'possibly' and 'perhaps'.
17:56 Wed 13th Nov 2013
Khandro, try this,( a thought experiment, not to be attempted by idiots in real life). Pour 1 litre of 4N hydrochloric acid into a plastic bucket, then pour 1 litre of 4N sodium hydroxide into the same bucket. The resulting explosion will have happened by chance. The little atoms will have found their soul mates without any help from a chemical dating agency. The result...salt water and a some heat. Just extend this principle to all the chemicals washing around in the primordial ocean. If chemicals can combine they generally do eventually.
Let's see if I have this right... an intelligent entity pours a chemical compound (meaning it has to be constructed) into another chemical compound, into and out of plastic buckets (probably requiring complicated coonstruction) to induce an explosionand that's supposed to be proof or demonstration of "chance"? Ok, I got it...
Clanad is a stranger to Brownian motion?
Likewise the notion that molecules, whilst whizzing around at surprisingly high speeds and taking their wiggly 'random walk' trajectories have remarkably low odds of scoring the 'direct hit' required to make the exchange of molecular components at all possible in the first place.
"Bucket chemistry" was a phrase I first (and last) heard at school and still raises a smile.
It is a reference to how bulk quantity is one way of counteracting the low odds of pairs of molecules meeting.
Compare with catalytic processes where one or both molecules binds to the catalyst. By keeping it it stationary, the odds of the second molecule colliding in the correct orientation and at the right speed increase.
Likewise the notion that molecules, whilst whizzing around at surprisingly high speeds and taking their wiggly 'random walk' trajectories have remarkably low odds of scoring the 'direct hit' required to make the exchange of molecular components at all possible in the first place.
"Bucket chemistry" was a phrase I first (and last) heard at school and still raises a smile.
It is a reference to how bulk quantity is one way of counteracting the low odds of pairs of molecules meeting.
Compare with catalytic processes where one or both molecules binds to the catalyst. By keeping it it stationary, the odds of the second molecule colliding in the correct orientation and at the right speed increase.
Hmm
Not sure you can say that in your example the explosion happened by chance Jomifl
true the paths taken by the atoms are non-deterministic but for the explosion to be a chance event there bust be some probability that if you did it enough times the explosion would not happen and I don't believe that is the case.
I'm sure there's a better analogy to be had
Not sure you can say that in your example the explosion happened by chance Jomifl
true the paths taken by the atoms are non-deterministic but for the explosion to be a chance event there bust be some probability that if you did it enough times the explosion would not happen and I don't believe that is the case.
I'm sure there's a better analogy to be had
Khandro,
Try taking evolution backwards from where we are now.
Go back over those billions of years, through all those millions of species come and gone, through all the geology and fossil records. homonids, dinosaurs, fish, trilobites. keep reducing it until all you are left with is some sort of primordial soup. All that time.
Which is more likely and which is improbable? A chemical reaction or a god.
Try taking evolution backwards from where we are now.
Go back over those billions of years, through all those millions of species come and gone, through all the geology and fossil records. homonids, dinosaurs, fish, trilobites. keep reducing it until all you are left with is some sort of primordial soup. All that time.
Which is more likely and which is improbable? A chemical reaction or a god.
jomifl; Stick with your schoolboy experiments and plastic buckets; why drag God into it? Likewise LG, - ever eager to bring in the mention of 'Abrahamic religions'. All I suggested was intervention by an unknown higher power, this need not be contrary to scientific analysis. I think jake and Karl Popper might agree.
Also Charlie Chan; "Mind like parachute, only work when open".
Also Charlie Chan; "Mind like parachute, only work when open".
Khandro,
Presumably you mainly mean the DNA, RNA and their partners in action- (non-self repicating) proteins and those special proteins: enzymes (organic catalysts).
There is no simple answer but it must include chemistry, optimum conditions and time.
Start simply at first with chemical reactions, like jomifil's bucket chemistry. Many elements are reactive with others through their electrons' tendency to pair or fill their outer orbitals. This means they have potential energy. Ideally potential energy is minimumised. So 2 Hydrogen atoms will react with 1 Oxygen, to yield water with the release of energy - this energy-release is evidence the overall potential energy is reduced if not minimised.
Along with this comes also a factor called hydrogen bonding. Here an "OH" bond tends to be electronically polariised to form "-OH...HO-" bonds or hydrogen bonds. Hence not only water's surface tension but the bonds which allow DNA bases to bond into a double but mirror images. Hence the double helix of DNA.
I'll stop there for now wihout promising anywhere near an answer but a thinking point to stat with maybe.
SIQ.
Presumably you mainly mean the DNA, RNA and their partners in action- (non-self repicating) proteins and those special proteins: enzymes (organic catalysts).
There is no simple answer but it must include chemistry, optimum conditions and time.
Start simply at first with chemical reactions, like jomifil's bucket chemistry. Many elements are reactive with others through their electrons' tendency to pair or fill their outer orbitals. This means they have potential energy. Ideally potential energy is minimumised. So 2 Hydrogen atoms will react with 1 Oxygen, to yield water with the release of energy - this energy-release is evidence the overall potential energy is reduced if not minimised.
Along with this comes also a factor called hydrogen bonding. Here an "OH" bond tends to be electronically polariised to form "-OH...HO-" bonds or hydrogen bonds. Hence not only water's surface tension but the bonds which allow DNA bases to bond into a double but mirror images. Hence the double helix of DNA.
I'll stop there for now wihout promising anywhere near an answer but a thinking point to stat with maybe.
SIQ.
@jomifl
//Hypo, I believe there a few more molecules in the ocean than in a bucket.
Was I being too subtle? //
Ahhmmm. Pass.
(on the subtlety angle, at least)
Certainly there are more molecules in an ocean but that brings in the problem of dilution. It's no use if you have one of the reagents on one side of the ocean and the other on the opposite side.
Or, on the molecular scale, a picometer's worth of miss is as good as a mile (if you'll excuse the mix of units). :-D
I guess the planet has to build up a critical concentration of the required molecules in its seas, lakes and ponds before the reaction rate can get anything much on the 'products' side of the equation.
All reactions being reversible, all complex chemicals having a natural tendency to break apart, life has been a long game of working against the processes of decay, borrowing energy* to build complexity.
Hard to say whether or not self replication is the sole logical upshot of this but, once the mechanism has been 'stumbled upon', it's pretty much unstoppable and, by the time organisms arise, all other chemicals in the soup are merely 'food'. Any alternative self-replicating mechanisms that ever existed likely got wiped out.**
* logically, this should make me a sun-worshipper (shrug)
** which is why it is worth searching for life on Mars, imho, to see if all that random stuff achieved self-replication a second time, but with differences in the details of the mechanism.
//Hypo, I believe there a few more molecules in the ocean than in a bucket.
Was I being too subtle? //
Ahhmmm. Pass.
(on the subtlety angle, at least)
Certainly there are more molecules in an ocean but that brings in the problem of dilution. It's no use if you have one of the reagents on one side of the ocean and the other on the opposite side.
Or, on the molecular scale, a picometer's worth of miss is as good as a mile (if you'll excuse the mix of units). :-D
I guess the planet has to build up a critical concentration of the required molecules in its seas, lakes and ponds before the reaction rate can get anything much on the 'products' side of the equation.
All reactions being reversible, all complex chemicals having a natural tendency to break apart, life has been a long game of working against the processes of decay, borrowing energy* to build complexity.
Hard to say whether or not self replication is the sole logical upshot of this but, once the mechanism has been 'stumbled upon', it's pretty much unstoppable and, by the time organisms arise, all other chemicals in the soup are merely 'food'. Any alternative self-replicating mechanisms that ever existed likely got wiped out.**
* logically, this should make me a sun-worshipper (shrug)
** which is why it is worth searching for life on Mars, imho, to see if all that random stuff achieved self-replication a second time, but with differences in the details of the mechanism.
Hypo, even molecules on the opposite side of the world can get together after a few billion years and of course with nothing to consume them the simple molecules produced by volcanoes and lightning strikes could have accumulated to produced relatively high concentrations. With no free oxygen until long after the appearance of life these molecules would have persisted for much longer than they would now.
Clanad, all I was attempting to illustrate was that chemicals that can react together, will do so given a combination of sufficient time and concentration. There was no 'guiding along a path', the only 'force' involved is sufficient heat to make the molecules move enough to collide. The rest is down to random collisions. What answer didn't I deign to give that you wanted to misunderstand?
I forget the source (New Scientist magazine) and the year (80s/90s?). All I can recall is that it was something about clay.
Superfine particles, massive surface areas, submicroscopic gaps between grains.
//even molecules on the opposite side of the world can get together after a few billion years //
I said "it's no use if", not that this was impossible. (grin)
//and of course with nothing to consume them the simple molecules produced by volcanoes and lightning strikes could have accumulated to produced relatively high concentrations. //
Agreed.
//With no free oxygen until long after the appearance of life //
Crucial point. A chloroplast's inner workings would make a Swiss watchmaker's head spin.
// these molecules would have persisted for much longer than they would now. //
I was alluding to the fate of complex molecules (enzyme levels of complexity) in the presence of heat, acids, alkali, salinity, other noxious organic chemicals.
Yes, extremophiles do exist and {} knows how their enzymes don't get cooked to bits but I think they evolved their way into boiling hot vents.
Confusingly, I also support the reverse view that deep ocean vents could support non-enzymic processes at reaction rates analgous to life and that organisms evolved their way up the water column. The emergence of enzymes and progressively more efficient versions of them meant regions of colder temps and/or lower water pressure became viable for exploitation.
Superfine particles, massive surface areas, submicroscopic gaps between grains.
//even molecules on the opposite side of the world can get together after a few billion years //
I said "it's no use if", not that this was impossible. (grin)
//and of course with nothing to consume them the simple molecules produced by volcanoes and lightning strikes could have accumulated to produced relatively high concentrations. //
Agreed.
//With no free oxygen until long after the appearance of life //
Crucial point. A chloroplast's inner workings would make a Swiss watchmaker's head spin.
// these molecules would have persisted for much longer than they would now. //
I was alluding to the fate of complex molecules (enzyme levels of complexity) in the presence of heat, acids, alkali, salinity, other noxious organic chemicals.
Yes, extremophiles do exist and {} knows how their enzymes don't get cooked to bits but I think they evolved their way into boiling hot vents.
Confusingly, I also support the reverse view that deep ocean vents could support non-enzymic processes at reaction rates analgous to life and that organisms evolved their way up the water column. The emergence of enzymes and progressively more efficient versions of them meant regions of colder temps and/or lower water pressure became viable for exploitation.
Meths in spaaaaaace.....
http://
Maybe we're a privileged planet, in that we didn't end up being pickled from on high?
http://
Maybe we're a privileged planet, in that we didn't end up being pickled from on high?
In my last contrbution I dealt only with the way a sequence of bases could after polymerisation could, via hydrogen bonding, form potentially mirror images and hence potentially self-freplicate. All easy stuff.
By shere coincidence (I see poor jomifil has come under fire every time he talks sense) I was now going to submit on the subject of the cell membrane.
Chemical reactions proceed faster when the constituent reactants are concentrated. So critical in the creation of life would have been the bagging-up of some of the early ingedients. This would be done via bags made mainly of phospholipids. These can be semi-permeable - letting chemicals in but not out. So such bags, formed randomly in the soup, were probably a key constituent in speeding up the creation of life. All very random but that's how chemistry works - random atomc or molecular collisions but at terrific speed. Those entities with a tendency to combine will do so and the nucleic acid bases will do so. But not adenine to guanine and thymine to cytosine, they require linkers made of phosphate and deoxyribose. Skip that - lipoid membranes are much more easily formed. They are now the containers within every living thing. The simplest life form is the bacterium, just one cell. Forget viuses they cannot replicate without invading a cell.
Oceans or a bucket, who knows how big the soup or separate soups were? But it/they contained literally countless common chemicals from which we derive (from the first bacteria of course).
SIQ.
By shere coincidence (I see poor jomifil has come under fire every time he talks sense) I was now going to submit on the subject of the cell membrane.
Chemical reactions proceed faster when the constituent reactants are concentrated. So critical in the creation of life would have been the bagging-up of some of the early ingedients. This would be done via bags made mainly of phospholipids. These can be semi-permeable - letting chemicals in but not out. So such bags, formed randomly in the soup, were probably a key constituent in speeding up the creation of life. All very random but that's how chemistry works - random atomc or molecular collisions but at terrific speed. Those entities with a tendency to combine will do so and the nucleic acid bases will do so. But not adenine to guanine and thymine to cytosine, they require linkers made of phosphate and deoxyribose. Skip that - lipoid membranes are much more easily formed. They are now the containers within every living thing. The simplest life form is the bacterium, just one cell. Forget viuses they cannot replicate without invading a cell.
Oceans or a bucket, who knows how big the soup or separate soups were? But it/they contained literally countless common chemicals from which we derive (from the first bacteria of course).
SIQ.
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