Does osmosis require a protein channel?
Normally, epithelial cells of mucous membranes express a chloride ion channel that allows movement of Cl- down its electrochemical gradient and out of the cell. This increase in extracellular electrolytes draws water out of the cells by osmosis, hydrating the mucus.

In cystic fibrosis, this protein is defective, most commonly caused by misfolding and subsequent degradation. Cl- cannot diffuse out of the cell and thus water is not drawn out, leading to thick mucus.




  ...given that CF changes the protein channels used for chloride ions to move through osmosis.


Water flows by osmosis, not ions.


  I thought osmosis was through a permeable membrane...


Osmosis does occur through permeable membranes, but large, bulk flow of water can be mediated by protein channels called aquaporins. Read more here.


  ...and active transport used a protein channel.


Active transport of solutes does use protein transporters, but they are not strictly "channels": "channel" is the term used for passive transport, also called facilitated diffusion when a channel is involved.