Question

The cystic fibrosis transmembrane conductance regulator (CFTR) is a transporter involved in

• A. Glucose transport
• B. Chloride ion transport
• C. Calcium homeostasis
• D. Amino acid uptake

Hint:

Think about which ion's movement across epithelial cells is disrupted in cystic fibrosis.

Answer 1

The Correct Option is B

Step 1: Recall what CFTR is.
CFTR stands for cystic fibrosis transmembrane conductance regulator, a protein channel sitting in the plasma membrane of epithelial cells.
It belongs to the ABC (ATP-binding cassette) transporter family, but unlike most ABC transporters that pump solutes using ATP, CFTR itself works as a gated ion channel once switched on by ATP binding and phosphorylation.

Step 2: Identify the ion it moves.
CFTR opens a pore that lets chloride ions (Cl-) cross the cell membrane, moving them out of cells lining the airway, gut, pancreas, and sweat glands.
This chloride movement pulls water along with it by osmosis, which keeps mucus on these surfaces thin and easy to clear.

Step 3: Connect this to the disease name.
When the CFTR gene is mutated, as happens in cystic fibrosis, chloride transport fails, so less water follows the ions, and the mucus produced becomes thick and sticky, clogging the lungs and pancreas.
This is why the disease and the gene are both named after this chloride-transport defect.

Step 4: Eliminate the other options.
Glucose transport across membranes is handled by GLUT transporters, not CFTR.
Calcium homeostasis relies on calcium pumps and calcium channels such as SERCA and voltage-gated calcium channels, separate proteins from CFTR.
Amino acid uptake uses its own dedicated family of amino acid transporters, again unrelated to CFTR.

Final Answer:
CFTR is a channel for chloride ion transport.
\[ \boxed{\text{Chloride ion transport}} \]