Cystic fibrosis results from a non-functioning CFTR (cystic fibrosis transmembra

Question

Cystic fibrosis results from a non-functioning CFTR (cystic fibrosis transmembrane conductance receptor). Loss of function of the receptor results in altered epithelial salt and water transport due to an inability of CFTR to transport chloride ion (Cl-). This loss of transport function has multi-system impacts, leading to a variety of pathologies associated with CF.

1) CF patients typically have difficulty performing moderate to heavy aerobic activities. Explain why this occurs by using your knowledge of the important link between cellular respiration and respiration (i.e., breathing).

2) Mutation of CFTR also has implications for the gastrointestinal and endocrine systems. Thickened mucus secretions within the pancreas impairs the ability to release important digestive enzymes. A thickening of pancreatic secretions is associated with poor growth and development. Apply your knowledge of the gastrointestinal system to explain the connection between decreased, thickened secretions and poor growth & development.

3) Thick mucus secretions in the pancreas may cause structural damage that is related to development of cystic fibrosis-related diabetes (CFRD). Explain diabetes and apply your knowledge of the endocrine functions of the pancreas to explain why CFRD develops.

Please please help me understand and connect these 3 situations

Explanation / Answer

Cystic fibrosis (CF) is an autosomal recessive disorder. The gene responsible for the cause of CF is cystic fibrosis transmembrane conductance regulator (CFTR) gene. The cytogenetic location of CFTR is 7q31.2. Mutation in CFTR receptor leads to accumulation of fluid in lung cells and made them osmotically imbalance.

Since, it an autosomal recessive disorder 1/4 (25%) the progeny will be effected (homozygous recessive) and 1/4 (25%) the progeny will be normal (homozygous dominant) and 1/2 (50%) of population will be act as carriers (heterozygous).  

1)

In a person with cystic fibrosis a defect occur in chloride channel protein, which interfere the uptake of Cl- ions and it indirectly interfere the uptake of Na+ ions. This situation leads to formation of thicker mucus in the respiratory lumen, which can cause chocking of respiratory canal and may lead the patient to death.

Due to obstruction in breathing, CF patient unable to intake more amount of oxygen. So, the cellular respiration would be inhibited (lack of oxygen results inhibition of aerobic respiration). Therefore, the synthesis of ATP decreases, which will weaken health condition of the patients due to lack of enough energy levels to meet the demand.

2)

The “Islets of Pancreas” contain four types of cells namely “alpha, beta, delta and F cells.” Alpha cells secrete glucagon and beta cells secrete insulin. Delta cells produce somatostatin, and F cells produce pancreatic polypeptide (PP) hormone. Bile, produced by the pancreas, contains bile salts that break up lipids into small droplets, making it easier to be further broken down into fatty acids and glycerol by a digestive enzyme called pancreatic lipase.

A thickening of pancreatic secretions results low secretion of insulin, glucagon and somatostatin and it is associated with poor growth and development. This is because absorption and digestion of glucose and fatty acids (the major metabolites) would be lowered. Due to lack of metabolites both catabolic (ATP or energy synthesizing metabolic reactions) and anabolic (growth promoting metabolic reactions) alerted, which results poor growth & development.

3)

Thick secretion of mucus lower the releasing of the hormone called insulin. So, impaired release of insulin results occurrence of Cystic fibrosis-related diabetes (CFRD). Insulin receptor is embedded in the plasma membrane, thus it is called transmembrane tyrosine kinase receptor.

This receptor is stimulated or activated by the hormone called insulin and other insulin like growth factors called IGF-I and IGF-II. The Insulin receptor mainly play role in the maintenance of blood glucose levels. If these receptors do not work properly due to structural damage, then the deficiency of these receptors leads to occurrence of a disease called diabetes.

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