Final answer:
Cholesterol is the main sterol in the human body, influencing cell membrane structure and serving as a precursor for various molecules, whereas lecithin is a phospholipid involved in lipid transport.
Step-by-step explanation:
The description of a sterol pertains to a category of lipid molecules that have a characteristic structure comprised of four interlocked hydrocarbon rings. Cholesterol is the primary sterol found in the human body and is indeed a sterol, not lecithin. Cholesterol functions importantly in the cell membrane, providing both rigidity and fluidity, and serves as a precursor for the synthesis of other essential molecules such as steroid hormones (testosterone, estrogen), bile salts, and vitamin D. In contrast, lecithin, or phosphatidylcholine, is a type of phospholipid necessary for the formation of lipoproteins, playing a crucial role in the metabolism and transport of lipids within the body.