Ergosterol

Ergosterol is a sterol found mainly in fungal cell membranes. Ultraviolet light converts it into previtamin D₂, which rearranges to vitamin D₂.

Fungal cell membrane: The lipid bilayer surrounding a fungal cell, containing sterols and other membrane components. Ergosterol is a major sterol in this membrane and helps shape its physical properties.
Amphotericin B: An antifungal drug that binds fungal membrane sterols and disrupts membrane integrity. Its binding to ergosterol helps explain its antifungal action and toxicity.
Steroid: A class of organic compounds built around a characteristic four-ring carbon skeleton. Ergosterol’s defining molecular framework is a modified steroid ring system.
Cholesterol biosynthesis: The pathway by which animal cells produce cholesterol from acetyl-CoA. It parallels fungal sterol synthesis but produces cholesterol through a different pathway.
Sterol: A class of lipids with a four-ring steroid structure and a hydroxyl group. Ergosterol belongs to this lipid family, whose members influence membrane organization.
Azole antifungals: A class of antifungal drugs that inhibit sterol 14α-demethylase. Azoles impair ergosterol production, weakening fungal membranes.
Cholesterol: The principal sterol in many animal cell membranes and a precursor to steroid hormones. It is the familiar animal counterpart to ergosterol, with a different side chain and membrane context.
Fungal plasma membrane: The membrane that separates a fungal cell’s cytoplasm from its surroundings. Its sterol composition is often ergosterol-rich, unlike many animal plasma membranes.
Fungal sterol biosynthesis: The pathway by which fungi synthesize sterols, including ergosterol, from acetyl-CoA. This pathway produces ergosterol through a sequence of enzyme-catalyzed reactions.
Terbinafine: An antifungal drug that inhibits squalene epoxidase in sterol biosynthesis. Blocking an early step in the pathway reduces downstream ergosterol production.

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