Cystic fibrosis results from a non-functioning CFTR. Loss of function of the rec

Question

Cystic fibrosis results from a non-functioning CFTR. Loss of function of the receptor results in altered transport of salt and water across the epithelial layer of the lung alveoli due to an inability of CFTR to transport chloride ions correctly. This loss of transport function has effects on many organ systems, leading to a variety of symptoms associated with CF.

-One of the most common genetic mutations respobsible for a defective CFTR is a 3 base pair deletion which results in an in-frame deletion of a single phenylalanine amino acid from the CFTR protein. Apply your knowledge of the central dogma and protein structure and function to explain how this deletion can result in a fully-synthesized CFTR which is inserted correctly into the epithelial membrane yet is non-functional.

- CF patients typically have difficulty performing moderate to heavy aerobic activities. Using your knowledge of cellular respiration and respiration (breathing) explain why this occurs.

-CF leads to production of extremely thick mucous in the lung aveoli. Use your knowledge of water/solute transport across membranes. Do you think that CFTR is no longer able to import Cl- or export Cl-?

-Apply your knowledge of the gastrointestinal system to explain the connection between decreased, thickened pancreatic secretions and poor growth and development.

-Apply your knowledge of the endocrine functions of the pancreas to explain why CFRD (cystic fibrosis-related diabetes) develops and possible consequenses of developing CFRD.

Explanation / Answer

Part 1-
Even if the protein is inserted into the epithelial membrane, absence of Phe will cause improper folding of the protein which will lead to non-functional receptor. That's why it will work at all.

Part 2-
This is because they have problem of heavy mucus in their respiratory tract, which leads to reduced level of O2 reaching the lungs and thus, people have difficulty in doing heavy aerobic exercises.

Part 3-
It will not be able to export Cl- ions, which will lead to preventing the flow of water molecules also to move outside the cells and clear off the mucus layer.

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