Question-   Briefly describe ( or draw) the structure of a phospholipid bilayer and explain the forces holding it  together. Why is it more stable to have membrane close up into a liposome rather than to have exposed edges?

Answer - Phospholipids bilayer - The two layers of phospholipids arranged in such a way that their hydrophobic tails are projecting inwards while their polar head groups are projecting on the outside surfaces.  Phospholipid bilayer structure forms the membrane that surrounds each of your cells and plays an important role in regulating cellular function.

> Vander Waals forces hold the hydrophobic tails of the phospholipid bilayer together and hydrogen bonds keep the hydrophilic heads of opposite the tails together as well as interact with water surrounding the bilayer.

>Because a  liposome encapsulates a region of aqueous solution inside a hydrophobic membrane and dissolved hydrophilic solutes cannot readily pass through the lipids.