Which of the following describes the function of lipids?

Lipids play a vital role in biological systems, primarily serving two key functions: energy storage and membrane structure. As a type of macromolecule, lipids are hydrophobic or nonpolar, which makes them particularly effective for storing energy. They can store more energy per gram compared to carbohydrates, making them a dense energy source for organisms. Additionally, lipids are essential components of cell membranes, where phospholipids form the bilayer structure that provides a barrier between the inside and outside of the cell. This bilayer is crucial for maintaining the integrity of the cell and regulating the movement of substances in and out.

The other options pertain to functions performed by different classes of biomolecules. For instance, information storage is primarily the function of nucleic acids, such as DNA and RNA. Regulating biochemical reactions is typically associated with proteins, particularly enzymes, which catalyze reactions within the body. The transport of nutrients is usually carried out by specific proteins known as transporters or channels, rather than lipids. Thus, the primary roles of lipids in energy storage and forming cellular structures make this choice the most accurate description of their function.