terpene biosynthesis sesquiterpene biosynthesis sesquiterpenoid biosynthesis pathway UPa:UPA00449 The formation from simpler components of sesquiterpenes. Sesquiterpenes are a class of terpenes that consist of three isoprene units and have the molecular formula C15H24. Like monoterpenes, sesquiterpenes may be acyclic or contain rings, including many unique combinations. Biochemical modifications such as oxidation or rearrangement produce the related sesquiterpenoids. GO:0051762