Water/Fat Solubility

[CoffeeintheMorning]

I understand that polar molecules require transport proteins to penetrate through membranes and non-polars are capable of going through the membrane without proteins.

If like dissolves like, meaning non-polar molecules dissolve non-polar molecules, why is it that fat-soluble molecules are able to penetrate through the membrane without being dissolved and are not dispersed into the fatty acid tails of the membrane?

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[aldol16]

It's because of the fatty acid tails that allow the small, nonpolar solutes to diffuse through, via the very principle of like dissolves like. The polar head groups aren't rigid - they move around. If there's just a small opening, a small, nonpolar solute like O2 can easily pass through into bilayer, where they are easily solvated by the nonpolar fatty acyl tails.

 

[deleted738762]

Plus a majority of the membrane is lipophilic, even though it's amphipathic.