Polarity of phospholipids and membrane function
Phospholipids are amphipathic, meaning that they both attract and repel water. The phosphate head attracts water (hydrophilic), and the fatty acid tail repels water (hydrophobic). This differs from most other lipids, which are entirely non-polar.
Cell membranes are made from a phospholipid bilayer.
The amphipathic nature of phospholipids allows for them to form a membrane. When exposed to an aqueous environment, the hydrophobic tails will face away from the aqueous environment while the hydrophilic heads will face the water.
This feature is key to the spontaneous assembly of the lipid bilayer of membranes. Phospholipids placed in an aqueous solution automatically form a membrane.
As shown in the image, phospholipids can also form liposomes and micelles in an aqueous environment.
Liposomes are employed in drug delivery. They are artificial vacuoles created by pharmaceutical industries.