isoprénoïde

Isoprenoids, also known as terpenoids, are a large and diverse class of organic chemicals that are produced naturally in many plants, animals, and microorganisms. They are derived from five-carbon isoprene units and are often characterized by the presence of multiple methyl branches. Isoprenoids play crucial roles in various biological processes and are involved in a wide range of functions, including electron transport, membrane stability, and light absorption.

The basic building block of isoprenoids is isoprene (2-methyl-1,3-butadiene), and they are classified based on the number of these isoprene units they contain. For example, hemiterpenes contain one isoprene unit, monoterpenes contain two, sesquiterpenes contain three, and so on. This classification continues up to tetraterpenes, which contain four isoprene units. Beyond this, isoprenoids can contain additional isoprene units and are often referred to as polyterpenes.

Isoprenoids are involved in numerous biological functions. In plants, they contribute to processes such as photosynthesis, where they act as accessory pigments in light-harvesting complexes. They also play a role in plant defense mechanisms, acting as toxins or feeding deterrents against herbivores. In animals, isoprenoids are involved in various physiological processes, including cell signaling and membrane structure. Some isoprenoids, like cholesterol, are essential components of animal cell membranes and are precursors to steroid hormones.

The diversity of isoprenoids is vast, with over 55,000 known structures. This diversity arises from the various combinations and modifications of the isoprene units. Isoprenoids are also of significant commercial interest, as they are used in the production of fragrances, flavors, and pharmaceuticals. Examples include menthol, used in various cooling agents, and artemisinin, a potent antimalarial drug. The study of isoprenoids continues to be an active area of research, driven by their biological importance and potential applications.