Which statement is false regarding ion channels?
a. Ion channels remain closed unless a ligand binds to it.
b. The purpose of ion channels is to stimulate signaling pathways utilizing the cell's polarization status.
c. Molecules such as Ca²⁺ , Na⁺ , K⁺ , or Cl⁻ pass through ion channels.
d. The direction of spontaneous ion flow across a polarized membrane depends on the ion's concentration gradient, as well as the electrical gradient.