[Campbell Biology P.270] Nerve growth factor NGF is a water-soluble signaling molecule, wher... | Practice Question

Nerve growth factor NGF is a water-soluble signaling molecule, whereas aldosterone is lipid-soluble. Based on their properties, why would NGF require a cell-surface receptor, while aldosterone utilizes an intracellular receptor?

  • 1: Water-soluble molecules are too large to pass through the plasma membrane, unlike lipid-soluble molecules.
  • 2: Lipid-soluble molecules can readily diffuse across the plasma membrane, allowing them to reach intracellular receptors.
  • 3: NGF needs a cell-surface receptor to amplify its signal, a function not required for aldosterone.
  • 4: Aldosterone's receptor is pre-bound to DNA in the nucleus, making it inaccessible to NGF.

Explanation

Lipid-soluble signaling molecules, like aldosterone, can freely diffuse across the lipid bilayer of the plasma membrane to reach receptors located in the cytoplasm or nucleus. Water-soluble molecules, like NGF, cannot easily pass through the plasma membrane and therefore require cell-surface receptors to transmit their signals.