How are phospholipids arranged in a bilayer?

Phospholipids are composed of a hydrophilic head (made up of phosphate and glycerol molecule), and 2 hydrophobic fatty acid tails (hydrocarbon chains).

The hydrophobic tails face inwards towards each other, hence are protected from the polar fluids, and the hydrophilic heads face outwards (in contact with cytoplasmic and extracellular fluids).

Phospholipids are arrange in a two layer structure. The phospholipids contains a head which is known as a 'hydrophilic' or water loving head. This part of the phospholipid will come into contact with any water. By contract, the tails of the phospholipid are known as hydrophobic or 'water hating'. they will arrange themselves so they are facing inwards and will not come into contact with any water. Because of these properties the bilayer is formed with the heads of the phospholipids facing outwards and the tails inwards.

Phospholipid bilayers have a hydrophilic head and hydrophobic tail.

Hydrophobic fatty acid tails are hydrocarbon chains and are positioned towards each other. Therefore, the hydrophilic heads face outwards (extracellular).