Cystic fibrosis is a disease caused by a defective gene on chromosome #7 in humans. This gene codes for a transport molecule (CFTR = cystic fibrosis transmembrane receptor) that is found in the cell membrane of cells and is involved with movement of water and chloride ions across the plasma membrane. These transporters are typically found in tissues lining ducts, including the breathing passages of the lungs and the organs that are involved with food digestion and absorption. In cells with a normally functioning CFTR molecule, this molecule moves chloride ions (with a negative charge) out of the cell to the covering mucus on the outside. Positively charged sodium ions then follow these chloride ions out of the cell to maintain electrical balance. This increases the total electrolyte concentration in the mucus, resulting in the movement of water out of the cell, and this water helps provide a fluid environment. People that have a defective gene (and thus a nonfunctioning CFTR molecule) produce abnormally thick and sticky mucus that builds up in the ducts and passageways. The buildup of this sticky mucus results in life-threatening lung infections and serious digestive problems. Many charged particles such as ions cannot pass directly across the plasma membrane. Thus, passive transport of the chloride and sodium ions occurs via what process?

Question

Quizplus · Accepted Answer

Facilitated diffusion is the process by which ions like chloride and sodium passively move across the plasma membrane with the help of transport proteins, such as the CFTR molecule, without the expenditure of energy.

Cystic Fibrosis Is a Disease Caused by a Defective Gene