Final answer:
Aquaporin is the channel protein that facilitates the rapid passage of water molecules through the cell's phospholipid bilayer, using a hydrated channel within the protein structure to allow for facilitated diffusion.
Step-by-step explanation:
The channel protein that allows a significant amount of water to pass through the selectively permeable phospholipid bilayer is known as Aquaporin. Aquaporins are integral transport proteins that specifically facilitate the rapid transit of water molecules across the cell membrane, making the process much more efficient than simple diffusion through the phospholipid bilayer.
While the bilayer's hydrophobic core impedes the passage of polar molecules, aquaporins provide a hydrated channel allowing for facilitated diffusion. These proteins are essential for maintaining the cell's water balance and contribute to various physiological processes. Due to the significance of their discovery, particularly their role in water balance, Peter Agre was awarded a Nobel Prize in Chemistry in 2003.