What are lipids primarily composed of?

Lipids are primarily composed of fatty acids, which are long hydrocarbon chains with a carboxylic acid group at one end. These fatty acids can be saturated or unsaturated, influencing the structure and function of the lipid. In various forms, such as triglycerides, phospholipids, and sterols, lipids play critical roles in energy storage, cell membrane structure, and signaling pathways within the body.

Other biomolecules mentioned, such as amino acids, carbohydrates, and nucleotides, serve different functions. Amino acids are the building blocks of proteins, carbohydrates are primarily used for energy storage and providing structural support, and nucleotides are the monomers of nucleic acids like DNA and RNA. While they are all vital to biological functions, they do not comprise the structure of lipids. Hence, the composition of lipids being primarily fatty acids is a defining characteristic of this biomolecule group.