Explain one structural feature OR one functional feature of lipids

Structural refers to features of its structure–how it is made. As examples, the monomers and the shape of the carbon backbone.
Structural Feature: Fatty Acid Chain Length

Lipids are composed of a hydrophobic (water-insoluble) fatty acid tail and a hydrophilic (water-soluble) head. The length of the fatty acid tail in a lipid can vary and can influence the physical properties of the lipid, such as its melting point. For example, long-chain fatty acids have a high melting point and tend to be solid at room temperature, while short-chain fatty acids have a low melting point and tend to be liquid.

Functional Feature: Phospholipid Bilayer

Phospholipids are a type of lipid that form the basis of cellular membranes, such as the plasma membrane. The functional feature of phospholipids is their ability to self-assemble into a lipid bilayer, which acts as a barrier and controls the movement of ions and molecules into and out of the cell. The hydrophobic fatty acid tails face inward, away from the water-based environment both inside and outside the cell, while the hydrophilic heads face outward, towards the aqueous environment. This arrangement creates a stable, fluid structure that allows cells to maintain their shape and perform their functions.