Osmosis

You enter the lab and take your sit next to your lab partner Tom.  Prof. Smith begins the lab practical by asking for the definition of Osmosis. You proudly raise your hand.

You: Osmosis is the movement of water molecules across the plasma membrane of the cell, depending on the solute concentration inside and outside of the cell. It is a passive transport process, just like diffusion. Therefore, water movement is from a high concentration of solute to a low concentration of solute.

Prof. Smith: Well done! The plasma membrane is made up of a phospholipid bilayer with embedded protein which have hydrophobic (water-loving) and hydrophilic (water-hating) sides.

From: Urry, L. A., Cain, M. L., Wasserman, S. A., Minorsky, P. V., Orr, R. B., & Reece, J. B. (2020). Campbell Biology (12th ed.). Pearson.

What is the main property of a plasma membrane called that facilitates the movement of small molecules or water molecules across the cell?