Which two monomers combine to create lipids?

Lipids are a diverse group of organic molecules that are largely nonpolar and hydrophobic. They play critical roles in biological systems, including energy storage, insulation, and forming cell membranes. The correct answer involves the combination of fatty acids and glycerol to form triglycerides, which are the most common type of lipid.

Fatty acids are long hydrocarbon chains that can be saturated or unsaturated, while glycerol is a three-carbon alcohol. When a glycerol molecule bonds with fatty acids through ester linkages, it results in the formation of triglycerides. The structure of triglycerides is crucial for their function in energy storage as they store much more energy than carbohydrates per gram. This is due to the highly reduced nature of fatty acids, making them efficient for energy storage in organisms.

In contrast, the other options involve different types of molecules that combine to form proteins (amino acids) or nucleic acids (nucleotides and sugars), which are not related to lipid formation. Thus, the combination of fatty acids and glycerol is specifically essential for the creation of lipids, making it the correct answer.