Facilitated Diffusion & Membrane Potential

Facilitated Diffusion Basics

• Movement of molecules from high to low concentration through transport proteins.
• Required for large/small polar molecules and charged ions.

Membrane Proteins & Transport

• Channel/carrier proteins: Facilitate diffusion of large/small polar molecules.
• Aquaporins: Allow large quantities of water to cross the membrane.
• Channel proteins: Necessary for charged ions ($Na^{+}$, $K^{+}$).

Membrane Polarization

• Occurs due to the movement of ions across the membrane.
• Establishes an electrochemical gradient and membrane potential (electrical potential difference).

Sodium-Potassium Pump

• Contributes to membrane potential maintenance.
• Uses metabolic energy ($ATP$) to pump $3$ $Na^{+}$ ions out and $2$ $K^{+}$ ions into the cell, both against their concentration gradients.
• Aids in establishing and maintaining concentration gradients and membrane potential.