Phospholipids in Water
Components of Phospholipid Molecule
Phosphate group
Charged/Polar
Hydrophilic i.e. wants to be in contact with water
Fatty acid chain
No charge
Hydrophobic i.e. wants to stay away from the water
Phospholipids in Water
At Low Concentration: Monolayer
At low concentrations, phospholipids make a layer on the surface of the water.
The phosphate group dips in the water.
The fatty acid chain protrudes in the air away from the water.
At High Concentration: Micelles
At high concentrations, phospholipid molecules assemble into spherical micelles.
The phosphate group makes the surface of the spare that comes in contact with water.
Fatty acid chains point towards the center of the sphere which is away from the water.
At Still Higher Concentration: Bilayers
At still higher concentrations phospholipids arrange into two parallel sheets in which fatty acid chains are facing each other.
The phosphate group is at the outer side of the bilayer in contact with water
Fatty acid chains are deep inside the bilayer, away from the water.
The membrane of cells and organelles is made by this type of interaction between phospholipid molecules and water.
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Now that you know the chemistry behind the formation of the membranes, we will study more about biological membranes in the next session.