What are lipids primarily composed of?

Lipids are primarily composed of fatty acids, which are long hydrocarbon chains, and glycerol, a three-carbon molecule. When fatty acids are attached to glycerol, they form triglycerides, which are the most common type of lipid found in the body. This structure allows lipids to serve various functions, including energy storage, insulation, and making up cell membranes.

The other answer choices involve components of different macromolecules. Amino acids and nucleotides are the building blocks of proteins and nucleic acids, respectively, while sugars and starches are carbohydrates, which are quite distinct from lipids in structure and function. Proteins and carbohydrates themselves are also different classes of biomolecules, further illustrating that the composition of lipids is specifically unique to the fatty acid and glycerol combination.