Answer:
Hydrophobic
Step-by-step explanation:
The structure of a cell membrane is that of a lipid bilayer consisting of a hydrophilic polar head and a hydrophobic (literally meaning water-hating) hydrocarbon tail.
The hydrophilic head group is a polar group, for example a sugar or choline molecule.
The hydrophobic tail consists of two fatty acid chains of between 14 - 24 carbons atoms. However, the most common fatty acids chains are those having 16 and 18 carbon atoms. Links in the tail arise if the carbon chain contains a cis- double bond. This serves to reduce the tight packing of the membrane and so increases membrane fluidity. The hydrocarbon tails are hydrophobic and non-polar and therefore do not form hydrogen bonds with water.
The overall function of the cell membrane is to serve as a selective barrier between the cell and its environment.