Biology transport across cell membrane

Hello, I have been revising transport across cell membrane and was wondering: are large/ polar molecules not able to move across the phospholipid bilayer at all, or is it just much slower if they do and so not effective?

Thank you! Hope this makes sense...

Reply 1

kaorimiyazono

They can't move across it at all. Large molecules are just too big to pass through, and polar molecules can't pass through because the fatty acid tails of the phospholipids are hydrophobic whereas polar molecules are hydrophilic and these properties do not mix.

Reply 2

biology234

(Original post by kaorimiyazono)They can't move across it at all. Large molecules are just too big to pass through, and polar molecules can't pass through because the fatty acid tails of the phospholipids are hydrophobic whereas polar molecules are hydrophilic and these properties do not mix.

Ah ok that makes sense, thank you