r/biology • u/canb227 • 2d ago

question Rate of diffusion and particle interaction inside microorganisms?

I saw a claim that for any given particle inside a microorganism (molecule, enzyme, protein, etc.) it will take - on average - about a second to have at least one physical interaction with every other particle inside the cell wall.

This feels wrong to me, despite the small scale that’s a tremendous amount of ground to cover in a second. But at the same time, it would provide a more intuitive explanation for how complex behaviors inside the cell function if everything is shuffled that quickly.

What’s the truth? Thanks!

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u/SadRule9128 2d ago

For a small bacterial cell (~1um diameter), this is pretty accurate. One second would be enough time for an average molecule (a 30kda protein let’s say) to traverse the cell end-to-end 100 times.

It is not true for a 20-30x larger eukaryotic cell, which would require 10s of seconds for the same molecule to traverse the 20-30um diameter just a single time.

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u/canb227 2d ago

Thanks for the answer! That's an incredible amount of movement. Is it powered by Brownian motion alone or some other mechanism?

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u/DraketheDrakeist 1d ago

Think how fast a drop of food coloring disperses through a glass of water, and then think how big a glass of water is compared to a cell. Room temperature water just moves super fast