Chemical evolution:

Discussion in 'Biology & Genetics' started by paddoboy, Aug 7, 2020.

  1. Q-reeus Valued Senior Member

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    I particularly emphasized any credible response to my challenge re explaining origin of a fully functioning integral cell membrane, should be free of empty rhetoric, bald assertions.
    There needs to be a detailed explanation that acknowledges the severe issue for unguided abiogenesis. One or two here ignore that and pretend it's all solved, at least in principle. BS.
     
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  3. iceaura Valued Senior Member

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    Everybody agrees with that.
    And maybe someday, after many decades of research, there will be.

    But detailed explication of stuff that happened nearly 4 billion years ago in tissues that do not fossilize easily and rocks that have mostly disappeared in tectonic recyclings will not be easy.

    Fortunately we already have some good theory, which has led to startling advances and discoveries - we already have good evidence and theoretical support for the "unguided" part, as well as the abiogenetic part, for example. That was fortunate, because the problems with the "guided" and " biogenetic" assumptions that dominated the field for thousands of years had pretty much squelched progress and made vast confusions - not only in that, but in biological research generally. So the rapid advances of the field since the late 1800s, and especially WWII, are not illusory.
     
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  5. Traverse Registered Member

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    This thread's topic's actually my favorite topic of all. I first met this field in 1986 as a wet-behind-the-ears undergrad. Initially, being more of a physical chemist, I was much taken by Pasteur's 1848 discovery of the homochirality of organic molecules derived from living things (i.e., versus the racemic versions of the same molecules whenever they were synthesised from scratch in the lab by a chemist). But now that I'm older, I've become an adherent of the "RNA World" conception for an origin of life on the early Earth.
     
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  7. Q-reeus Valued Senior Member

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    Trying to put those two aspects together, are you then satisfied with a natural explanation for origin of necessarily homochiral notionally self-replicating RNA in that primeval RNA world? Any links to where the issue is claimed to be solved?
     
  8. Xelasnave.1947 Valued Senior Member

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    I am not here to argue but I saw a great video last night an it had a tested mechanism for formation of cell membrane I recall...I will see if I can find it and look again get some names etc..but I am sure they said that the cycling of warm pools both of light and water concentration was the answer...sorry I could not be more helpful but I was listening to it to fall asleep so you can understand why so patchy.

    Anyways very much enjoying this thread.

    Alex
     
  9. Traverse Registered Member

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    I expect that the advent of our chiral bias (e.g., D-carbohydrates & L-amino acids) will have been simply due to a chance occurrence, sans any physical effect (e.g., polarized light, magnetism, etc.) having directed/dictated such.
     
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  10. Traverse Registered Member

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    Based on basic principles in Surface Chemistry, I don't actually see original membrane formation (& therefore primitive compartmentalization/cellularization) to be a crucial difficulty in the origin-of-life field. It's actually the origins of the various metabolic reactions/cycles and of the genetic system that are crucial problems to be addressed. Intellectually, the membranization bit is already effectively a non-issue here.
     
  11. exchemist Valued Senior Member

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    That's interesting. You wouldn't happen to have a reference to something I can read about early membrane formation, would you? (Like you, I can handle a bit of chemistry.)
     
  12. Q-reeus Valued Senior Member

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    Have you worked out the probability that inherently racemic or just mostly racemic concatenations can give rise to homochiral RNA strands several hundred base units long? Try 1 in 2^200.
    Any known realistic prebiotic inorganic 'chiral template' surfaces are weakly chiral in effect. So that value will be a good approximation. Further, where does the requisite information content required for self-replication come from? Not from some inorganic 'chiral template' surface with its regularly repeating crystal structure.
     
  13. Q-reeus Valued Senior Member

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    A non-issue? Please elaborate. I'm assuming you have read the previous posts on that matter. While you're at it, here's a checklist of problems in general for unguided abiogenesis:
    https://www.godandscience.org/evolution/chemlife.html
    Let us know if most or even one of the itemized issues has a credible nature-only solution. Note the extensive references linked to.
     
  14. Traverse Registered Member

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    You might perhaps enjoy the 1990s Chem.Evol. book by S.F. MASON. 1960s work by S. FOX and others would interest you. Much membranization stuff has been done, & it photographs nicely for papers & slides. Essentially, a bright high school kid knows enough basic Surface Chemistry to 'get it' (esp. "hydrophilic heads" versus "hydrophobic tails"), and the biomembrane challenges remaining are really in the presumably 'downstream' details of the membraning (& liquid crystallizing) molecule types, and the formations of ion/molecular channels through the membrane, and of the various intra-membranal proteins.
     
    Last edited: Jan 16, 2021 at 11:06 AM
  15. Xelasnave.1947 Valued Senior Member

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  16. Q-reeus Valued Senior Member

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    Why? I can guess but best if you give a sensible answer. Btw here is the bio of Rich Deam the author of most if not all articles there:
    https://www.godandscience.org/apologetics/testimony.html
    I've made it clear before, compartmentalized thinking doesn't preclude accuracy and competence in one area living alongside illogical thought in another.
     
  17. Traverse Registered Member

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    On the math front, you're actually limiting yourself to just primary structure; one needs to consider how higher order (viz. secondary, tertiary, & even quaternary) oligomeric molecular structures can fall into lower chemical potential energy wells if chirally-biased.

    Yes, inorganic (esp. mineralogic) surfaces are generally weak in chiroselectivity, so that tells one that Life's chiral bias will more likely have had an organic (higher-order structural chemical potential energetic) origin in terms of something like a protein-folding (& hence enzymatically active) chemical evolutionary advantage.

    The informational content that you want will have originated 'downstream' in chemical evolutionary terms.
     
    Last edited: Jan 16, 2021 at 11:09 AM
  18. Traverse Registered Member

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    I think that I could 'hold my own' against all comers.
     
  19. Q-reeus Valued Senior Member

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    From what I have gleaned, primitive RNA 'self-replicators' are typically modeled as just simple strands. Where there is no differential in potential well for left vs right handed peptide unit attachments.
    How is that not skirting a chicken-egg paradox in both cases?
     
  20. Q-reeus Valued Senior Member

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    Well that was an easy out!

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  21. Xelasnave.1947 Valued Senior Member

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    I cant express myself very well on this but in my view to relate anything to religion is a bit of a non event given there is no evidence for the super natural and so everything must proceed upon literally a guess... we can never have a scientific theory that can include the supernatural ..take intelligent design it can never become a theory...best to prove god and so far that has never been done.
    Alex
     
  22. Q-reeus Valued Senior Member

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    Yes I know how passionately you hate the notion of a god. Are you sure there is no underlying emotion-driven reason that automatically somehow links god to unsavory religious practices?
    You make an absolute pronouncement there re 'no evidence' that imo is totally unwarranted. But I guess we all have faith-based issues of one sort or another.
     
  23. Traverse Registered Member

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    Yes, the simplest ribozymes are indeed of the order of only ~50 nucleotides long, but their ribozymic chemical activity depends on them being able to fold just right. On the second matter, you don't make any sense. Quoi?
     

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