<unk>  is any of a<unk> ass of certain organic molecules. A<unk>  is a sterol (or modified steroid), a type of lipid.<unk>  is biosynthesized by all animal cells and is an essential structural component of animal cell membranes. When chemically isolated, it is a yellowish crystalline solid.<unk>  also serves as a precursor for the biosynthesis of steroid hormones, bile acid and vitamin D.<unk>  is the principal sterol synthesized by all animals. In vertebrates, hepatic cells typically produce the greatest amounts. It is absent among prokaryotes (bacteria and archaea), although there are some exceptions, such as Mycoplasma, which require<unk>  for growth. François Poulletier de la Salle first identified<unk>  in solid form in gallstones in 1769. However, it was not until 1815 that chemist Michel Eugène Chevreul named the compound "cholesterine".
Cholesterol
Lipoprotein
Oxycholesterol
Glycogen
Phytosterol
Saturated fat
Protein 
Medium-chain triglyceride