What property of fatty acid molecules allows them to repel water?

Fatty acid molecules are characterized by long hydrocarbon chains, which are composed mainly of carbon and hydrogen atoms. This structure makes the majority of the fatty acid non-polar, meaning they do not have a significant partial positive or negative charge. As a result, fatty acids do not interact favorably with water, which is a polar molecule.

The hydrophobic property of fatty acids is key to their behavior in biological systems, particularly in the formation of cell membranes where they aggregate to form bilayers. This arrangement shields their hydrophobic tails from water while the hydrophilic heads interact with the aqueous environment. Such properties explain why fatty acids repel water and aggregate in biological systems, forming structures essential for cellular function.