What is the role of receptors in mediating steroids and protein hormones?

Steroid hormones are lipids; they can cross directly through the cell's plasma membrane and nuclear membrane, binding to receptors. Receptor – hormone complex is formed and serves as a transcription factor; it promotes or inhibits the transcription of certain genes

Protein-based hormones (application on epinephrine) Epinephrine binds to a receptor called the G-protein receptor on the plasma membrane

G-protein activates adenylyl cyclase, converting ATP to cAMP (secondary messenger).

cAMP (second messenger) is a small water-soluble molecule that can quickly spread through the cytoplasm and relay signals throughout cells.