amphipathic

An amphipathic, or amphiphilic molecule contains both nonpolar hydrophobic and polar hydrophilic groups.

The hydrophobic group can be a long carbon chain, of the form: CH3(CH2)n, where n is greater than 4 and less than 16. Biologically important amphoteric molecules are the phospholipids, one of the main constituents of biological membranes, which naturally form bilayers. The phospholipid cell membrane insulates the cells from the surrounding medium.