Which of the following statements correctly describes the interaction between a signaling ligand and its receptor?
- A) Lipid-soluble ligands diffuse across the plasma membrane to bind intracellular receptors, whereas hydrophilic ligands bind to cell-surface receptors.
- B) Hydrophilic ligands diffuse directly through the phospholipid bilayer to bind cytosolic receptors without requiring transmembrane proteins.
- C) Ligands typically form permanent covalent bonds with receptor active sites to maintain continuous pathway activation.
- D) A specific ligand produces identical physiological responses in all target cells regardless of receptor subtype or internal machinery.
