Why Is the Phospholipid Bilayer Impermeable to Ions?

💡 The Answer

• The hydrophobic interior of lipid tails creates a high energy barrier for charged particles.
• Ions would need to shed their hydration shell, which costs over 200 kJ/mol of energy.
• This impermeability allows cells to maintain steep electrochemical gradients for Na+, K+, and Ca2+.
• Ion channels and pumps provide regulated pathways, making the bilayer a perfect electrical insulator.