The monomer building block unit of lipids is generally considered to be fatty acids and glycerol.
Fatty acids are long hydrocarbon chains with a carboxyl group at one end, whereas glycerol is a three-carbon alcohol. Together, these components form the basic structure of many lipids, including triglycerides, which are the primary form of fat stored in the body.
When a glycerol molecule bonds with three fatty acids, they create a triglyceride. This process involves dehydration synthesis, where water is released as the bonds form. Therefore, while lipids do not have a single monomer like carbohydrates (which have monosaccharides), the combination of fatty acids and glycerol serves as the fundamental building blocks for most lipids.