Phospholipids are pretty similar to triglycerides, except one of the fatty acid molecules is replaced by a phosphate group. The phosphate group is hydrophilic (it attracts water molecules) and the fatty acid tails are hydrophobic.
structure
A) phosphate group
B) glycerol
C) tail of fatty acids
Phospholipids are found in the cell membranes of all eukaryotes and prokaryotes.
They make up what's known as the phospholipid bilayer.
Phospholipid heads are hydrophilic and their tails are hydrophobic, so they form a double layer with their heads facing out towards the water on either side.
The centre of the bilayer is hydrophobic, so water-soluble substances can't easily pass through it -the membrane acts as a barrier to those substances.
