Final answer:
Lipids are vital in organisms for energy storage and providing insulation, as well as being a key component of cell membranes and hormones.
Step-by-step explanation:
Role of Lipids in Organisms: Lipids are a crucial category of biological macromolecules that perform many functions within organisms. Among these, the most notable roles of lipids include energy storage and providing insulation from the environment for both plants and animals. These macromolecules are important constituents of cell membranes and are vital in forming the hydrophobic barrier that protects the integrity of cells. Lipids are also involved in forming the structure of many hormones and act as signaling molecules. Therefore, the correct answer to the role of lipids in most organisms is A. Energy storage and insulation.