Question

Cystic fibrosis is a genetic disorder caused by a mutated cystic fibrosis transmembrane conductance regulator (CFTR) protein. This protein is important for controlling the exchange of materials in the gas -exchange and digestive systems. the defective protein is no longer able to properly move chloride ions from the inside of the cell to the outside. Because of this water balance is negatively affected, leading to a buildup of thick mucus secretions outside of the cells. Victims of CF suffer from lung infections and digestion difficulties Which statement best describes the physiological problem faced by those with CF?

A) A faulty CFTR protein is unable to create a hypertonic environment on the outside of the cell

B) Without a functioning CFTR protein water cannot be transported across the membrane

C) The CFTR protein is required to establish a higher concentration of chloride ions on the inside of the cell

D) When the movement of the chloride ions is compromised, the cell cannot create a hypotonic environment on the outside of the cell, thus creating conditions for a thick mucus layer

Answer 1

CFTR is a Cystic Fibrosis Transmembrane Receptor. It is an ABC-transporter and functions by using ATP to remove Cl- ions outside the cell.

Therefore, the CFTR is mutated, the Cl- ions can no longer be transported outside effectively. This results in the buildup of Cl- inside the cell. As a result, there is an osmotic imbalance that forces the water from outside the cell to inside to account for the increased chloride concentration. In this process, the extracellular space is depleted of water thereby making it thick and mucous rich.

The role of CFTR is to release Cl- ions outside. This results in the concentration of Cl- being built up outside the cell that triggers the water to flow outside. This function is compromised here.

Hence, the correct option is d.