Cholesterol, from the Ancient Greek chole- (bile) and stereos (solid) followed by the chemical suffix -ol for an alcohol, is an organic molecule. It is a sterol (or modified steroid),[4] a lipid molecule and is biosynthesized by all animal cells because it is an essential structural component of all animal (not plant or bacterial) cell membranes that is required to maintain both membrane structural integrity and fluidity. Cholesterol enables animal cells to dispense with a cell wall to protect membrane integrity and cell viability, thus allowing them to change shape and move about (unlike bacteria and plant cells which are restricted by their cell walls).
In addition to its importance for animal cell structure, cholesterol also serves as a precursor for the biosynthesis of steroid hormones and bile acids.[5] Cholesterol is the principal sterol synthesized by all animals. In vertebrates the hepatic cells typically produce greater amounts than other cells. It is absent among prokaryotes (bacteria and archaea), although there are some exceptions such as Mycoplasma, which require cholesterol for growth.[6]