Final answer:
The option that is NOT an example of facilitated diffusion is oxygen transport, as oxygen can diffuse directly through the cell membrane due to its nonpolar nature, without the aid of transport proteins.
Step-by-step explanation:
The question at hand is asking which item listed is NOT an example of facilitated diffusion. Facilitated diffusion is a type of passive transport that involves substances moving across the cell membrane via special transport proteins without the expenditure of cellular energy (ATP). These transport proteins include channel proteins and carrier proteins. For instance, GluT1 glucose transporters transfer glucose into cells, an anion exchange protein moves ions like Cl⁻ across the membrane, and channel proteins typically allow ions to pass through the membrane based on their size and charge. Furthermore, aquaporins are specialized channel proteins that facilitate the passage of water.
However, oxygen transport across the cell membrane occurs through simple diffusion due to its nonpolar nature and small size, making it soluble in the lipid bilayer of the cell membrane. This process does not require transport proteins, distinguishing it from facilitated diffusion.