What is the primary function of fats in biological systems?

The primary function of fats, also known as lipids, in biological systems is to serve as energy storage. Fats are highly efficient molecules for storing energy; they contain long hydrocarbon chains that yield a significant amount of energy when metabolized. This stored energy can be utilized by organisms during periods of low energy intake or increased energy demands.

Fats also play critical roles in cellular structure and function, such as forming the cell membrane's lipid bilayer, but their predominant role as energy storage is vital for maintaining metabolic functions. The energy stored in fats is much greater per gram compared to carbohydrates or proteins, making them an efficient energy reservoir for organisms.