Despite a lot of bad press, cholesterol remains an essential and important biomolecule in animals. As much as half of the membrane lipid in a cellular membrane is cholesterol, where it helps maintain constant fluidity and electrical properties. Cholesterol is especially prominent in membranes of the nervous system.
Cholesterol also serves as a precursor to other important molecules. Bile acids aid in lipid absorption during digestion. Steroid hormones all derive from cholesterol, including the adrenal hormones that maintain fluid balance; Vitamin D, which is an important regulator of calcium status; and the male and female sex hormones. Although humans wouldn't survive in one sense or another without cholesterol metabolites, cholesterol brings with it some well‐known side effects. Doctors find cholesterol derivatives, being essentially insoluble in water, in the deposits (plaque) that characterize diseased arteries.