Theory 28/Cellular/Cell polarity
Polarity Is Reaction Against Diffusion
The claim
Cell polarisation occurs above a threshold in the ratio of cortical reaction rate to cytoplasmic diffusion, so a fast-cycling protein can polarise in a large cell.
01Mechanism
A polar cap forms when the protein concentrates faster than diffusion erases the gradient; the ratio sets whether a stable domain exists.
02Prediction
Polarity should appear above a ratio threshold.
03Refutation
Polarity tracking protein amount would remove diffusion.