Squalene is a thirty-carbon unsaturated hydrocarbon, , with six carbon–carbon double bonds.[ref] Its long chain can be folded and cyclized during the biosynthesis of sterols, making it a useful connection between an acyclic precursor and complex fused-ring structures.
The sequence and geometry of the double bonds matter: they determine which groups can approach during a cyclization. Biological pathways use enzymes to control that geometry and the reaction cascade. Hydrogenation of the double bonds changes the compound's identity, rather than merely purifying the original squalene.
