Question

Why are receptors for steroid hormones located inside the cell rather than on the membrane surface?

Answer 1

Steroid hormones are built around a cholesterol backbone, which is a lipid. Since the majority of the thickness of the cell membrane is composed of hydrophobic fatty acid tails, steroid hormones, also being hydrophobic (or lipophilic), can easily pass through the cell membrane to seek out intracellular/extranuclear receptors. This process allows these types of hormones to bypass the membrane-coupled second messenger systems (G-protein/cAMP/IP3, etc.) to more quickly and effectively initiate their effects on the nucleus or other internal component(s) of the cell.