Question

facilitated diffusion is a process that occurs in plant and animal cells. as the name presumes, facilitated diffusion is a form of diffusion, but slightly different. this process is controlled by protein channels that are embedded into a cell’s membrane to escort the molecules inside of the cell.
if a desired molecule is too large or charged, instead of it moving through a cell’s membrane, it will travel through its designated protein channel into the cell.
facilitated diffusion utilizes these protein channels. there are hundreds of different protein channels for different molecules.
which one of the following molecules would be most likely to travel by facilitated diffusion?
a large, charged molecule
a tiny inorganic molecule
a molecule of oxygen

Explanation:

To determine the molecule that travels by facilitated diffusion, we refer to the text: "If a desired molecule is too large or charged, instead of it moving through a cell’s membrane, it will travel through its designated protein channel into the cell." A tiny inorganic molecule (like water, though not specified here, but tiny ones can diffuse freely) and oxygen (a small gas) can move through the cell membrane without protein channels (simple diffusion). Only large, charged molecules need the protein channels of facilitated diffusion.

Answer:

a large, charged molecule