What is the primary sterol in the fungal cell membrane that azoles target?

• A. Cholesterol
• B. Ergosterol
• C. Lanosterol
• D. Squalene

Answer: (B)

The primary sterol in the fungal cell membrane that azoles target is ergosterol. Ergosterol plays a critical role in maintaining the integrity and functionality of the fungal cell membrane, similar to how cholesterol functions in human cells. Azole antifungals work by inhibiting the enzyme lanosterol 14α-demethylase, which is involved in the biosynthesis of ergosterol. By disrupting the production of ergosterol, azoles compromise the structural integrity of the cell membrane, leading to increased permeability and ultimately, cell death.

Cholesterol is the major sterol in human cells, not fungi, and therefore is not the target of azole antifungals. Lanosterol is an intermediate in the biosynthesis pathway of ergosterol but is not the primary sterol present in the fungal cell membrane that is targeted by azoles. Squalene is another precursor in the sterol biosynthesis pathway that occurs before the conversion to lanosterol and subsequently to ergosterol, but it is not the primary target for the action of azoles. Therefore, the emphasis on ergosterol's role highlights its significance in fungal biology and the mechanism of action of azoles as antifungal agents.