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Biology might not be quantum, but its math is quantumlike

123 points · 60 comments · pseudolus

  1. __MatrixMan__ · · focus · HN ↗
    I feel like "is biology quantum?" gates are kept in a needlessly stringent way.

    They say that biological systems are too warm for quantum coherence to persist long enough to have meaningful effects. But if you have some molecule whose conformation is in a superposition of states--however briefly--and then the environment causes it to decohere and take on some fully determined non-quantum shape... that actual shape is still one of many possible ones into which it did not decohere. The environment has still hacked probability to trigger decoherence into this shape and not some other one, and evolution leans on this.

    If you took a classical bag and filled it with classical locks and classical keys and just shook it around for a while, none of those keys would end up in the locks. But because of this quantum lubricant, ligands binding receptors do find themselves in the appropriate conformation to facilitate signal transduction, even at low concentrations. It's absolutely astounding that it works at all, and in a fully classical world it wouldn't for the same reason that the keys don't end up in the locks when you shake the bag for a while.

    Biology is plenty quantum, and the people who are here to tell you it isn't are citing the abundance of interactions as evidence that it is not quantum, but it's through those many interactions that its quantum nature expresses itself.

    Maybe it's not spooky-action-at-a-distance style quantum. Maybe it's not indeterminate enough for this theoretical purpose or that one. If you're trying to cram god in there, well it might not be quite spooky enough for that, but so much of what happens in the macroscopic world would not happen if the quantum world were not as strange as it is, and that's doubly true for biology.

    1. jryb · · focus · HN ↗
      Your key and lock analogy is simply incorrect. Those interactions can be modeled with classic electrochemistry and are super predictive - the specificity is driven by evolution, not quantum mechanics. I mean sure, every system is technically quantum mechanical but those effects are never explored afaik.

      There are even educational demonstrations where people shake bags of 3D printed proteins with magnets (including competing proteins) and you end up with the expected structure.

      1. __MatrixMan__ · · focus · HN ↗
        classic electrochemistry has plenty of quantum effects baked into the parameters of the theory, it just doesn't bother to explain them in quantum terms.

        I'll have to look up those demonstrations. I know if I were making such a thing I'd stack the deck in favor of a good demonstration and I'd stick to very simple interactions. But if they've given the potential for random useless tangles a fair shake I'll have to rethink my position.

        If somebody has made some analog of ATP synthase which operates in this way it would be just fantastic to behold.

        Although if I did relax this position, I'd then be in need an explanation for why all of biochemistry feels like it takes place in some kind of cartoon universe. Like, maybe I've failed to put my finger on the reason, but I can't shake the feeling that the world being presented in biology class is just a little too cute to be this one.

        1. jryb · · focus · HN ↗
          I think the problem might be that you're looking for a description of reality that's truly fundamental, but that's not the goal of most biologists. The point of a minimal model is to make it easy to reason about a system and efficiently make predictions. It's a practical approach done for the sake of time and money. If it takes me weeks to plan an experiment using a QM model instead of a day with a classical one, and I end up doing the same thing anyway, what's the point?

          >Although if I did relax this position, I'd then be in need an explanation for why all of biochemistry feels like it takes place in some kind of cartoon universe. Like, maybe I've failed to put my finger on the reason, but I can't shake the feeling that the world being presented in biology class is just a little too cute to be this one.

          Here's one possible explanation for this feeling. Consider the alternative world: any time you write a paper about a protein, you have to measure its interactions with every other biomolecule that's present in the cell of interest. Then, you need to model all of those interactions simultaneously. You probably couldn't do that in 10 lifetimes. It's just not practical to do this, so you never read about it. Papers and textbooks necessarily present things in an overly focused way.

          So any paper you read has some...selection bias? If you're trying to find a zinc finger that binds some particular DNA sequence, and you find one and it has nanomolar affinity, you don't need to worry about what happens when that ZF binds actin or RNA polymerase or some phospholipid. We already know from the fact that it has nanomolar affinity for its target DNA that it isn't being sequestered by anything else in any measurable way. But its affinity for actin or whatever isn't zero - there IS a number, and they DO interact - it's just that it's incredibly weak and transient, so you're not going to notice it incidentally. Biology may seem cute because the ugly version would cost 20,000x as much to produce.

      2. timschmidt · · focus · HN ↗
        > every system is technically quantum mechanical but those effects are never explored afaik

        Photosynthesis depends on quantum behavior: <a href="https:&#x2F;&#x2F;www.youtube.com&#x2F;watch?v=rvFMBRnR3ms" rel="nofollow">https:&#x2F;&#x2F;www.youtube.com&#x2F;watch?v=rvFMBRnR3ms

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