If the lipid bilayer is at least 108 times less permeable to K ions than it is to water, then a way that this much needed ions can get into the cell is through ion channels.
Ion channels are memberane proteins that form pores and they also span across the cell membrane allowing ions to pass through these pores. They act as a passage through which charged ions can pass through. There are three main type: voltage-gated, extracellular ligand-gated, and intracellular ligand-gated ion channels.
