Thread

Biology might not be quantum, but its math is quantumlike

123 points · 60 comments · pseudolus

__MatrixMan__ · 1790482592 · 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. dnautics · 1790522915 · focus · HN ↗
  > 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
  I think you are vastly underestimating the number of collisions required to get an enzyme binding event. We did a back of the envelope calculation in grad school and it was something like >> 10^6 ~ 10^9.
  And you can of course do macroscopic things like this:
  <a href="https://www.youtube.com/watch?v=3X6qEE2fHvE" rel="nofollow">https://www.youtube.com/watch?v=3X6qEE2fHvE
  1. __MatrixMan__ · 1790525917 · focus · HN ↗
    Capsid assembly is a good example if you want to make a macroscopic analog that works over less than geologic time, but the next step is for the assembled capsid to find and ingest a nucleic acid containing a viral genome as it floats around a broth containing all sorts of other nucleic acids.
    It's wildly nonintuitive that this manages to happen. Maybe you're right, and it can be explained by the numbers being so tremendously large that they break intuition without the need to import any nonintuitive quantum weirdness.
    But if so, isn't such an explanation problematic in its own right? It banishes:
    > The quantum world is impossibly nonintuitive, and it's having an effect
    in favor of
    > The scales here are impossibly nonintuitive, and that's having an effect
    Like... we're still shoving the explanation under a rug, it's just now it's a different rug. Either the quantum effects explanation or the large numbers explanation needs further development before we can call this phenomenon adequately explained, and rather than doing that development it seems like the whole field is dedicated to championing their favored side as-is.
    dnautics · 1790530903 · focus · HN ↗
    What are you talking about. The phenomena are adequately explained. I can measure a Kd and make mathematically modeled predictions that will come true. I can even phenomenologically test contributions to the Kd (ablate hydrogen bond, delete or add a charge, etc)
    Nature is under no obligation to make explanations trivial to a human brain conditioned on quotidian macroscopic observation. Doesn't mean you have to appeal to quantum woo. We know more or less how much "quantum mechanics" (for some definition of QM, obviously an electron shell is QM, but for all intents and purposes you can just treat it as a classical ball that does a few weird things like bonding) contributes, to, say reaction rates. It's nonzero. It's nearly zero, though.
    __MatrixMan__ · 1790532277 · focus · HN ↗
    Nature is not, but scientists are. A theory which humans can map onto experiences at their scale and use to make predictions via intuition is superior (for use by humans) to a theory which makes accurate predictions for inscrutible reasons--supposing their predictive power is equivalent. Beauty, I guess they call it. It leads to improved decision making, experimental design, etc.
    dnautics · 1790533612 · focus · HN ↗
    As a working scientist: chasing beauty is not a good way to do science.
    > It leads to improved decision making, experimental design, etc
    It does not. It often does the exact opposite.
  2. ravila4 · 1790526801 · focus · HN ↗
    Exactly, and the classical lock and key analogy ignores electromagnetic and hydrophobic/hydrophilic interactions, which we can fully model in classical molecular dynamics systems
    dnautics · 1790531059 · focus · HN ↗
    That's not correct. Lock and key absolutely does take into account em and hydrophobic interactions. Also, molecular dynamics is nearly useless at modeling these things (which is why heuristic models such as alphafold, Rosetta, dominate)

Open on Hacker News to reply ↗

Unofficial Hacker News client; not affiliated with Y Combinator.