2.5.1.21 Biosynthesis of secondary metabolites - 01110 2.5.1.21 cholesterol biosynthesis cholesterol biosynthesis - 2.5.1.21 Metabolic pathways - 01100 2.5.1.21 Sesquiterpenoid and triterpenoid biosynthesis - 00909 2.5.1.21 Steroid biosynthesis - 00100