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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.


Next >>

Now that you know the chemistry behind the formation of the membranes, we will study more about biological membranes in the next session.


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