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canadianer
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Your question is rooted in a misundertsanding of the hydrophobic effect: hydrophillic and hydrophobic molecules do not repel but, rather, attract one another through van der Waals interactions. Instead of some repulsive force, the hydrophobic effect is actually driven entropically. I don’t think I will go into this in detail since it has been explained well in many places. That said, it is also explained very poorly in many places (which I suspect you have encountered). I recommend this website to learn about it and other intermolecular interactions.

Once you have a firm grasp on that, consider that in order for a hydrophobic molecule to reach a plasma membrane, it must already be solvated by water. The transfer of a hydrophobe from one hydrophillic environment (water) to another (head groups of the phospholipids in the plasma membrane) should be energetically negligible. The limiting step for passive diffusion across a membrane is transfer from the hydrophillic environment of the phospholipid head groups to the hydrophobic environment of their tails. In fact, the rate of diffusion across a plasma membrane increases with hydrophobicity.

canadianer
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