1. Energy Storage: Lipids, particularly fats and oils, are incredibly efficient energy storage molecules. They store more than twice the energy per gram than carbohydrates, making them ideal for long-term energy needs in organisms.

2. Cell Membrane Structure: Phospholipids are a crucial component of cell membranes. Their unique structure, with a hydrophilic (water-loving) head and hydrophobic (water-fearing) tails, allows them to form a bilayer that acts as a barrier, regulating what enters and exits the cell.