Ergosterol is a type of sterol, a lipid molecule, primarily found in the cell membranes of fungi, including yeasts, and some protozoa.
This compound is biologically significant as it serves as the direct precursor for the synthesis of Vitamin D.
When ergosterol is exposed to ultraviolet (UV) radiation, it undergoes a photochemical reaction. This process initiates the conversion of ergosterol into previtamin D2, which subsequently isomerizes to form Vitamin D2, also known as ergocalciferol.
Therefore, ergosterol is the essential precursor of Vitamin D.