CFTR protein transporting ions across lung membrane, illustration - stock illustration

Illustration of a cystic fibrosis transmembrane conductance regulator (CFTR) protein (blue) transporting chloride (Cl-) and bicarbonate (HCO3-) ions across the membrane (orange) of a lung epithelial cell. The energy for the CFTR to open is provided by ATP (adenosine triphosphate, red). The cell interior is top and the exterior is below. Genetic mutations can cause CFTRs to form incorrectly and remain closed, or not form at all, causing the condition cystic fibrosis. When CFTRs can not open, ions accumulate within cells. The absence of these ions from the cell exterior causes a lack of water around epithelial cells as water is drawn to areas of concentrated ions via osmosis. Epithelial cells in the lungs excrete mucus, and without sufficient water this becomes thick, sticky and difficult for the body to remove. This can cause difficulty breathing and increase the risk of lung infection