The key component of a lipid that distinguishes it from carbohydrates is the presence of fatty acids and glycerol. Lipids, which include fats, oils, and phospholipids, are characterized by long hydrocarbon chains that allow them to be hydrophobic (insoluble in water). In contrast, carbohydrates are made up of sugar molecules and are primarily hydrophilic (soluble in water). The unique structure of lipids makes them essential for energy storage, membrane formation, and signaling within biological systems.