Final answer:
Cholesterol belongs to the class of biological molecules known as lipids since it is soluble in organic solvents like ether and not in water.
Step-by-step explanation:
Based on the fact that cholesterol is soluble in ether, an organic solvent, but not in water, it is classified as a lipid. Lipids are defined by their solubility properties rather than specific functional groups. While carbohydrates are characterized by specific functional groups, lipids are largely hydrophobic and are more soluble in organic solvents than in water. This group includes not only fats and oils but also phospholipids, steroids like cholesterol, and other compounds that incorporate functional groups derived from various substances. Cholesterol is known for being an important component of cell membranes and a precursor to steroid hormones, underscoring its classification within the lipid category.