Chapter 9, Problem 5RQ

What property prevents the ligands of cell-surface receptors from entering the cell?

1. The molecules bind to the extracellular domain.
2. The molecules are hydrophilic and cannot penetrate the hydrophobic inferior of the plasma membrane.
3. The molecules are attached to transport proteins that deliver them through the bloodstream to target cells.
4. The ligands are able to penetrate the membrane and directly influence gene expression upon receptor binding.