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 a passive transport process in which water molecules, acting as a solvent, move across a semipermeable membrane from a region with a lower solute concentration (hypotonic) to a region with a higher solute concentration (hypertonic). This process aims to balance solute concentrations on both sides of the membrane.

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?