What does ergosterol mean?
Ergosterol is a sterol — a waxy, fat-like molecule — found in the cell membranes of fungi and certain protists, where it plays the same structural role that cholesterol plays in animal cells: keeping the membrane fluid and stable. Because humans neither produce nor require ergosterol, it makes an ideal target for medicine. Many important antifungal drugs, such as amphotericin B and the azoles, act by binding to ergosterol or by blocking the enzymes fungi use to manufacture it, thereby disrupting fungal membranes while leaving human cells largely unharmed. Ergosterol also has a nutritional significance: when exposed to ultraviolet light it undergoes a chemical change that converts it into vitamin D2 (ergocalciferol), which is why irradiated yeast was historically used as a vitamin D supplement. Outside the laboratory, the word belongs mainly to biochemistry, pharmacology, and food science, where measurements of ergosterol are often used to estimate fungal growth.
nounA sterol found in fungi and some protists that serves as the fungal equivalent of cholesterol in animal cell membranes. When exposed to ultraviolet light, it is converted into vitamin D2 (ergocalciferol).
- (biochemistry) A sterol occurring in the cell membranes of fungi and some protists, acting as the fungal analogue of cholesterol; on UV irradiation it is converted to vitamin D2.
"Fungal cell membranes rely on ergosterol in much the same way that animal membranes depend on cholesterol."
"Many antifungal drugs work by blocking the enzymes fungi need to synthesise ergosterol."
"The yeast culture was analysed for its ergosterol content as an indicator of membrane health."
Rarely used in the plural; as an uncountable chemical substance, ergosterol normally appears in the singular.
"Different fungal species contain slightly different membrane sterols."
Yeast can't make vitamin D — but sunbathe its membranes and the ergosterol inside turns straight into it.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of ergosterol
Ergosterol derives from 'ergot', the name of the fungus Claviceps purpurea from which the compound was first isolated, combined with '-sterol', the standard chemical suffix for sterols (itself a blend of 'stera' from Greek 'stear', meaning fat or tallow, and '-ol' denoting an alcohol). The word entered scientific English in the late nineteenth century following its identification in ergot and later in yeast. It shares the '-sterol' element with cholesterol, whose own name combines Greek 'chole' (bile) with the same suffix.
Related word forms
How ergosterol is actually used
A technical term used almost exclusively in biochemistry, microbiology, pharmacology, and food science; rare in everyday conversation. In medical and mycological writing it appears chiefly in discussions of antifungal drug mechanisms, fungal biomass estimation, and vitamin D2 production.
Easily confused with ergosterol
Cholesterol is the sterol of animal cell membranes, whereas ergosterol performs the equivalent role in fungi and is converted to vitamin D2 rather than D3.
Ergocalciferol (vitamin D2) is the product formed when ergosterol is irradiated with ultraviolet light.