Here's an answer that might help you! I hope this helps! :) Small uncharged polar molecules, such as H2O, also can diffuse through membranes, but larger uncharged polar molecules, such as glucose, cannot. Charged molecules, such as ions, are unable to diffuse through a phospholipid bilayer regardless of size; even H+ ions cannot cross a lipid bilayer by free diffusion.
water is a charged molecule so it CANNOT GET THROUGH THE LIQUD PART OF BILAYER. In order to allow water to move in and out cells have special protiens that act as a doorway
