ANATOMY

Detailed explanation-1: -Some signaling molecules are able to cross the plasma membrane and bind to intracellular receptors in the cytoplasm or nucleus, whereas most bind to receptors expressed on the target cell surface.

Detailed explanation-2: -The ligand crosses the plasma membrane and binds to the receptor in the cytoplasm. The receptor then moves to the nucleus, where it binds DNA to regulate transcription.

Detailed explanation-3: -Once outside the cell, they bind to transport proteins that keep them soluble in the bloodstream. At the target cell, the hormones are released from the carrier protein and diffuse across the lipid bilayer of the plasma membrane of cells.

Detailed explanation-4: -Which of the following signal molecules does not interact with cell surface receptors? Sol: (d) Testosterone.