 Examples of isoprenoids include carotene, phytol, retinol (vitamin A), tocopherol (vitamin E), dolichols, and squalene.Heme A has an isoprenoid tail, and lanosterol, the sterol precursor in animals, is derived from squalene and hence from isoprene.The functional isoprene units in biological systems are dimethylallyl pyrophosphate (DMAPP) and its isomer isopentenyl pyrophosphate (IPP), which are used in the biosynthesis of naturally occurring isoprenoids such as carotenoids, quinones, lanosterol derivatives (e.g.