Osmosis is the movement of water molacule through the plasma membrane through diffusion and facillitated diffusion is movement of polar molacules through the plasma membrane with the help of carrier proteins .So if water is a polar molacule then how it can diffus through the membrane like in the osmosis ? Is osmosis also termed as facilitated diffusion ?

Dear student,
Osmosis is not facilitated diffusion because osmosis is the movement of water molecule from higher to lower concentration through semipermeable membrane. But facilitated diffusion is the movement of ions or molecules from higher to lower concentration through carrier proteins.
Osmosis is especially defined for movement of water molecule but facilitated diffusion is defined for ions and molecules which can pass through channels or carrier proteins.
Cell membrane is selectively permeable due to presence of lipid molecule which contains hydrophilic and hydrophobic region which thus allows the diffusion of hydrophobic molecule and small polar molecule like water.


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