Terpenes, Terpenoids and Steroids: Properties, Biosynthesis and Functions

Terpenes belong to the largest class of secondary metabolites consisting of five carbon isoprene units which are assembled through innumerable patterns generating diverse structural motifs. Terpenes are linear or cyclic hydrocarbons, whereas terpenoids are oxygen-containing terpene analogues found in all living organisms. Steroids are a subclass of terpenoids that are biosynthesized from terpene precursors. Terpenes, terpenoids and steroids are all derived from five-carbon isoprene units assembled and arranged in different ways generating thousands of structurally varied molecules. Terpenes and terpenoids are widely explored as biomaterials and biofuels while steroids are used as drugs to increase protein synthesis in animals besides their anti-inflammatory, anticancer and other properties. In this chapter, we discuss the properties, functions and biosynthesis of terpenes and terpenoids in general and steroids in particular to better understand their functions and prospective applications.