The tail of a phospholipid is hydrophobic due to its chemical structure. Phospholipids are composed of a hydrophilic (water-attracting) ‘head’ and two hydrophobic (water-repelling) ‘tails.’ The tails are primarily made up of long hydrocarbon chains.
Hydrocarbon chains consist mainly of carbon and hydrogen atoms, which do not interact favorably with water molecules. Water is a polar solvent, meaning it has a distinct positive and negative end, leading to strong interactions with other polar substances. In contrast, hydrocarbons are nonpolar and do not form hydrogen bonds with water. This lack of polarity makes them repellent to water, resulting in the hydrophobic nature of the tails.
In a biological context, this property is crucial for the formation of cell membranes. The hydrophobic tails clump together to avoid contact with water, while the hydrophilic heads face outward, interacting with the aqueous environment. This arrangement is fundamental to forming the lipid bilayer, which is essential for cell integrity and function.