Biological isoprene unit. See

Biological isoprene unit. See Isopentenyl pyrophosphate Biosynthesis... 

Essential oils of many plants and flowers are obtained by distilling the plant with water. The water-insoluble oil that separates usually has an odor characteristic of the particular plant (rose oil, geranium oil, and others). Compounds isolated from these oils contain multiples of five carbon atoms (that is, 5, 10, 15, and so on) and are called terpenes (some compounds of this type were described on page 222). They are synthesized in the plant from acetate by way of an important biochemical intermediate, isopentenyl pyrophosphate. The five-carbon unit with a four-carbon chain and a one-carbon branch at C-2 is called an isoprene unit (see A Word About... Biologically Important Alcohols and Phenols, in Chapter 7). 

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