Phospholipid

Phospholipids are lipid molecules which have a phosphate group attached.

They are highly abundant in cell membranes, where they form a lipid bilayer, due to the amphiphatic nature of their hydrophilic heads and hydrophobic tails ^[1]. The majority of atoms in the hydrophobic tails are nonpolar and have no charge, this is what makes them insoluble when dissolved in water. However, the hydrophilic heads are soluble in water due to the presence of either charged groups which are electrostatically attracted to the water molecules, or polar groups which enable hydrogen bonds to be form between the heads and the water molecules ^[2].

References

1. ↑ Alberts et al. (2002) Molecular Biology Of The Cell, 4th edition, New York: Garland Science. p62
2. ↑ Alberts et al. (2008) Molecular Biology Of The Cell, 5th edition, New York: Garland Science. p620