[spacetimeuser5]

>>When we say voltage gradient, think the traditional ions and the like. But also think of the voltage gradient that a protein can have too, with binding pockets and stuff. Think voltage gradients that are held in place by lipid rafts on the membrane too. Think also the osmotic potential that ion concentration will have, not just the raw total voltage of a voltmeter. There are a lot of components, and therefore gradients, that make up the voltage potential.

It seems that both Claude and you use "voltage gradient" and "ion gradient" interchangeably, which may be not technically correct enough. In electrical engineering voltage = potential = charge difference btw 2 points = the driving force that drives a current to "flow" from a point of bigger potential to a lesser one (typically). Thus it is voltage (or a field) that will drive an ion or any charge gradient.

[Balgair]

Ah, a kinematics issue.

Yes, ions and charges will flow in Bio too, but that flow is generally restricted and used somehow. Nature is always finding a way to take a toll. Cells will also set up a voltage difference to accomplish things too, all on their own.

Like, cells are quite happy to make massive charge differences (for their size) and then use that to do some little thing. Generally, they use ATP to skit around those pesky little entropy issues to act like Maxwell's Demon.

Like, they are using ion flow/current and deciding how that will benefit them. They gate it, on and off, to induce all kinds of signaling and meiosis and energy transferring.

So, in Bio, a voltage/ion gradient isn't really thought of as the same way in EE. Like, we care about 10 or so K+ ions, that little of a difference can do all sorts of things for a cell. ANd the voltage potentials can be titanic, because the distance are so small. That Van Der Wals force man, you don't think it do, but it do.

One important and subtle thing I learned going from my engineering/physics background and into bio is not assume that cells are little micro machines. They are in fact alive. They study you back, in their own limited ways. They try very hard to stay alive too. So, when bio people talk about cells doing things, we really do mean that they have agency.

[spacetimeuser5]

I read one neurosurgeon (developing a theory of quantum biology) tell that mitochondria can develop voltage potentials comparable to a lightning bolt. Then searched a bit in PubMed and found something like still up to a couple of hundreds or a hundred milliVolts.

But I was curious, what do you think about the ways by which ligands find their receptors inside or outside cells in a dense bioelectrical and biochemical environment (as described here [0]). When I asked on stackexchange, they gave me a link about gradients and concentrations, but my question was about the very beginning of ligand's effect when it needs to find and activate at least one receptor. And no receptors seem to be able to "sense" a piece of space with a ligand's concentration, as they need direct binding of a ligand, but before this how does a ligand find a way to the receptor?

This may differ whether its a small or large molecule ligand, but my ligands of interest are ions (Ca/Mg, Na, K ,Cl; Li), peptides, anticancer drugs with metallocomplexes, ion channel drugs and similar drugs.

[0] https://news.ycombinator.com/item?id=35854316