Squalene

Squalene is a 30-carbon triterpene hydrocarbon found in plants, animals, and humans. It is a key intermediate in the biosynthesis of sterols, including cholesterol.

Squalene epoxidase: An enzyme that oxidizes squalene to 2,3-oxidosqualene during sterol biosynthesis. It adds the oxygen that enables squalene’s subsequent cyclization.
Triterpene: A class of compounds built from six isoprene units, usually containing 30 carbon atoms. Squalene is a linear hydrocarbon member of this larger chemical class.
Cholesterol: A sterol in animal membranes and a precursor for steroid hormones, bile acids, and vitamin D. Squalene supplies the carbon skeleton from which cholesterol is synthesized.
Sterol: A class of lipids with a characteristic four-ring structure and a hydroxyl group. Squalene is a precursor to sterols rather than a sterol itself.
Oxidosqualene cyclase: An enzyme that converts 2,3-oxidosqualene into cyclic triterpenes. It folds and cyclizes squalene’s oxidized derivative into a sterol framework.
Isoprene: A five-carbon diene that forms the basic structural unit of many natural isoprenoids. Squalene’s 30-carbon skeleton can be traced to six isoprene units.
Phytosterol: A plant sterol structurally related to cholesterol and common in seeds, nuts, and vegetable oils. Plants convert squalene into phytosterols through cycloartenol.
Ergosterol: The principal sterol in fungal cell membranes and a precursor of vitamin D2. Fungi synthesize ergosterol through a pathway that begins with squalene.
Lanosterol: A tetracyclic triterpenoid that serves as an intermediate in cholesterol biosynthesis in animals and fungi. It is the first sterol formed along the animal pathway downstream of squalene.
Isoprenoid: A broad family of natural and synthetic compounds assembled from five-carbon isoprene units. Squalene belongs to this family through its isoprenoid-derived carbon skeleton.

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