List the features of molecules that can cross or cannot cross the lipid bilayer. • List the major ions unevenly distributed across the cell membrane. Describe the process of depolarization and hyperpolarization

Features than can cross the lipid bilayer easily

• small

• uncharged

• hydrophobic

• gases (o2, CO2)

• some small lipophilic molecules

Features that cannot cross the lipid bilayer

• ions

• charged molecules

• polar molecules

• most hydrophilic molecules

Major ions unevenly distributed across the cell membrane

Inside high: K⁺ , negatively-charged proteins

Outside high: Na⁺ , Cl⁻ , Ca²

Depolarization

membrane potential becomes less negative (moves toward zero; Na⁺ in)

Hyperpolarization:

membrane becomes more negative (K⁺ out or Cl⁻ in)