isoprenoïde

Isoprenoids, also known as terpenoids, are a large and diverse class of organic compounds derived from units of isoprene, a five-carbon molecule. These compounds are found in virtually all living organisms, from bacteria and fungi to plants and animals. In plants, isoprenoids play a crucial role in many physiological processes, including photosynthesis, respiration, and defense against herbivores and pathogens. They are responsible for many of the characteristic scents and flavors of plants, such as the aroma of pine trees or the taste of mint.

The basic structural unit of an isoprenoid is isoprene (2-methylbuta-1,3-diene). Isoprene units can be linked together in various ways to form molecules of increasing complexity. For example, two isoprene units combine to form monoterpenes (C10), three units form sesquiterpenes (C15), four units form diterpenes (C20), and so on. Larger structures, such as carotenoids and steroids, are built from many isoprene units. The chemical structures of isoprenoids can be linear, cyclic, or branched, and they often contain oxygen-containing functional groups like alcohols, aldehydes, and ketones, which further increases their diversity.

Beyond their biological functions, isoprenoids have significant economic importance. Many essential oils, which are rich in monoterpenes and sesquiterpenes, are used in the fragrance and flavor industries. Diterpenes include important compounds like vitamin A and gibberellins, a class of plant hormones. Steroids, which are tetraterpenoids, encompass vital biomolecules such as cholesterol and hormones like testosterone and estrogen, as well as pharmaceuticals. Carotenoids, the longest isoprenoids, are important pigments in plants and animals, including beta-carotene, which is a precursor to vitamin A.