Steroid
A lipid with a characteristic four-ring carbon skeleton. Steroids include cholesterol, bile acids, and hormones such as cortisol and testosterone.
Steroid nucleus: The four fused carbon rings that form the structural core of most steroids. Its fused rings are the defining scaffold of the steroid class.
Steroidogenesis: The biosynthesis of steroid hormones from cholesterol through enzyme-catalyzed reactions. It shows how cells build hormone steroids from the common steroid precursor.
Steroid hormone: A signaling molecule derived from cholesterol that binds intracellular receptors to regulate physiology and gene expression. This subtype carries signals between endocrine tissues and target cells.
Triterpene: A terpene built from six isoprene units, often serving as a precursor to sterols and other natural products. Triterpenes are broader precursors, while steroids have a characteristic fused-ring skeleton.
Cholesterol: A membrane lipid and precursor to steroid hormones, bile acids, and vitamin D. It is a prominent steroid and the starting material for many others.
Cytochrome P450: A family of enzymes that oxidize many molecules, including intermediates in steroid synthesis and breakdown. Several members catalyze key modifications in steroid hormone pathways.
Corticosteroid: A steroid hormone produced by the adrenal cortex, or a drug modeled on one. Corticosteroids regulate stress responses, metabolism, and inflammation.
Terpenoid: A chemically modified terpene or a related compound assembled from isoprene-derived units. Steroids share biosynthetic ancestry with this larger family of natural products.
Lipid: A broad group of water-insoluble or partly water-insoluble biological molecules, including fats, oils, and sterols. Steroids belong to this wider class of hydrophobic biological molecules.
HMG-CoA reductase: The enzyme that catalyzes the rate-limiting step in cholesterol biosynthesis. Its pathway supplies cholesterol from which steroid hormones are made.