[extropy-chat] HISTORY: Solved & Unsolved Riddles

The Avantguardian avantguardian2020 at yahoo.com
Sat Nov 8 14:00:33 UTC 2003





> > 3. Why is all life on earth asymmetric at a molecular level. The amino
> > acids that make up proteins on earth all have a "left-handed"
> > (levorotary) chirality and the sugars that make up carbohydrates are
> > "right-handed" (dextrorotary). [snip]
>
Rafal Smigrodzki <rafal at smigrodzki.org> wrote:### Probably no need to invoke the stellar dust, since the asymmetry is a
direct consequence of the mechanics of biological macromolecule synthesis.
An enzyme, ribosome or nucleic acid polymerase can recognize only a limited
number of molecular species (just like a lock can recognize only a limited
number of keys, all of the same general symmetry), and the moiety that forms
the most rigid part in a polymer, the backbone, can only assume a limited
number of conformations.

*Correct- but you are putting the cart before the horse, unless you are proposing that either enzymes or ribozymes came somehow into being whole-cloth without some form of stochastic polymerization event from their monomer constituents. Are you suggesting a Special Creation event? I would not be terribly mortified if this is what you were suggesting since if I walked into a room and saw thousands of coins all showing heads, despite knowing that there is a finite none-zero probability that they fell that way by pure chance, I would find the hypothesis that "someone" arranged them that way to be the more probable hypothesis. Eleizer, what say you, oh disciple of Bayes? *

Using a standard conformation for the backbone of
all monomers saves on the number of enzymes needed to make all the
components, and the standard conformation for aminoacids just happened to be
the L-conformation.

*Yes, and a standardized hardware configuration, operating system, and programming language would save much money, time, and effort by IT professionals the world over. But game theory predicts there will be two or more standards, e.g. Macs vs. PCs or Unix vs. Windows vs Applesoft, that in a competitive enviroment will reach a Nash equilibrium with one another which incedently is the observed case. Note I would not be so surprised if even a huge majority of life forms used one "chiral standard or the other" but the fact that it is entirely a single standard strikes me as highly improbable and wondrous.*     

Of course, if there were any imbalances in the concentration of one
enantiomer in the primordial soup, that enantiomer would be much more likely
to become the standard...

*ok, now both thermodynamically and game theory wise, it is easy to see how a completely imbalanced asymmetric system might over time evolve into either a chemical or a Nash equilibrium. For example it is easy to imagine a perfectly ordered system of all reactants or all products becoming a chemical equilibrium of both, even if products vastly outweigh the reactants, but you would still have some reactant present at any given temperature. Likewise lets say in game theory you have a system composed entirely of doves, then hawks having such a huge advantage in such a population would quite naturally evolve. Likewise doves will arise in a pure population of hawks (since the hawks will kill one another while the doves wont). Yet going the other way is much less credible. It is easier to believe that Pepsi arose simply to compete with Coke's former monopoly and stole market share from it, than to believe that if Coke and Pepsi started out with equal market share that someday one would buy
 the other out and gain a monopoly.*  

one way or another, a standard had to choose itself.
* Are you suggesting that in a former Spirit World Conference chaired by the RNA Fairy the amino acid spirits got together and passed an unanimous resolution calling for them to all become left-handed from that day forward? Was the Esteemed Reverend Sun Yung Moon privy to those proceedings or is that just hear-say?* <wicked grin>  







The Avantguardian 


"He stands like some sort of pagan god or deposed tyrant. Staring out over the city he's sworn to . . .to stare out over and it's evident just by looking at him that he's got some pretty heavy things on his mind."

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