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

This question asks what CFTR actually moves across the cell membrane, based on what its name and its role in disease tell us.

1. Glucose transport: sugar uptake into cells is carried out by GLUT-family carrier proteins, a completely different set of transporters from CFTR.
2. Chloride ion transport: CFTR forms a channel in the cell membrane that, once switched on by ATP and phosphorylation, lets chloride ions flow out of epithelial cells, exactly what its full name, chloride conductance regulator, describes.
3. Calcium homeostasis: calcium levels inside cells are controlled by dedicated calcium pumps and calcium channels, not by CFTR.
4. Amino acid uptake: this job belongs to specific amino acid transporter proteins, again unrelated to CFTR's function.

Because faulty chloride transport through CFTR is exactly what causes the thick mucus seen in cystic fibrosis patients, the protein's core job must be chloride ion transport.

Let's summarize:

• CFTR is a chloride channel found in epithelial cell membranes.
• Loss of its chloride transport activity, not any glucose, calcium, or amino acid role, is what causes cystic fibrosis.

So the correct answer is chloride ion transport.