How Do Ion Channels Select Which Ions Pass Through the Membrane?

💡 The Answer

• Ion channels have narrow selectivity filters that match size and charge of specific ions.
• Potassium channels use a backbone carbonyl-lined filter to strip water from K⁺ ions.
• Sodium channels have a different filter geometry that excludes larger potassium.
• Selectivity is often based on precise atomic interactions within the pore.
• This allows nerve cells to generate action potentials with incredible speed.