The cystic fibrosis transmembrane conductance regulator (CFTR) protein helps to maintain the balance of salt and water on many surfaces in the body, such as the surface of the lung. When the protein is not working correctly, chloride -- a component of salt -- becomes trapped in cells. Without the proper movement of chloride, water cannot hydrate the cellular surface. This leads the mucus covering the cells to become thick and sticky, causing many of the symptoms associated with cystic fibrosis.
