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Learning Objectives

Learning Objectives. 05 September 2014. What causes cystic fibrosis Explain the role of the CFTR protein in regulating mucus moisture Explain why CF sufferers cannot control the moisture in their mucus. Key Words – Cystic fibrosis transmembrane receptor protein Channel proteins

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Learning Objectives

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  1. Learning Objectives 05 September 2014 • What causes cystic fibrosis • Explain the role of the CFTR protein in regulating mucus moisture • Explain why CF sufferers cannot control the moisture in their mucus. • Key Words – • Cystic fibrosis transmembrane receptor protein • Channel proteins • Active transport • Diffusion

  2. How cystic fibrosis affects the lungs Sticky mucus builds up in the airways, reducing flow of air into alveoli. Lungs gradually fill up with mucus, making them less effective for gas exchange. Symptoms: • Severe coughing - to remove excess mucus. • Breathlessness - shortage of oxygen increases tiredness and lack of energy • Infections - as bacteria are trapped in mucus

  3. How does cystic fibrosis affect the reproductive systems?

  4. How cystic fibrosis affects the digestive system: Thick, sticky mucus blocks the pancreatic duct preventing enzymes from reaching the duodenum.Food is not digested and absorbed sufferers fail to put on body mass and suffer malnutrition. Trapped digestive enzymes damage the pancreatic cells affecting cells producing insulin resulting in diabetes.

  5. What does the CFTR protein do? It helps control the viscosity (or stickiness) of mucus that lines the epithelial cells of the airways, digestive and reproductive systems mucus cilia epithelial cell If the mucus in airways is… too sticky: the cilia cannot beat and remove the mucus, which then clogs up airways too runny: the mucus can flood the airways

  6. When there is excess water in the mucus Water is drawn out of the mucus and it thickens Cl- Na+ H2O mucus 2 5 apical membrane CFTR channel closed Na+ channel open H2O pump 1 basal membrane 4 3 tissue fluid H2O Cl- Na+

  7. When there is too little water in the mucus Water is drawn out of the mucus and it becomes less sticky Cl- Na+ Na+ mucus 3 2 4 apical membrane Na+ channel closed CFTR channel open The CFTR somehow blocks the sodium channels H2O Cl- 1 H2O basal membrane 5 pump tissue fluid H2O Na+

  8. With cystic fibrosis The mucus becomes very thick and sticky Cl- Na+ H2O mucus 1 2 3 X apical membrane The CFTR protein cannot block the sodium channels so they are always open CFTR non- functional Water drawn out by osmosis Na+ channel open H2O basal membrane tissue fluid H2O Cl-

  9. Check your answers!

  10. CFTR protein and membrane transport 1. Na+is actively pumped across the basal membrane (bottom part). 2. Na+ diffuses through sodium channels in apical membrane (top part). 3. Cl- diffuses down electrical gradient (basal end of cell becomes more positively charged due to Na+). 4. Water is drawn out of cells by osmosis due to high salt concentration in tissue fluid (basal end). 5. Water is drawn out of mucus by osmosis.

  11. CFTR protein and membrane transport • Cl- is pumped into the cell. • The CFTR channel is open so Cl- ions diffuse through to the mucus. • Na+ then diffuses down the electrical gradient (area of negative charge) into the mucus. • There is a high concentration of salt in the mucus so water leaves the cell and enters the mucus by osmosis. • Water from the basal end of the cell is drawn into the cell by osmosis.

  12. Use your knowledge of functioning CFTR proteins to explain why CF patients cannot control their mucus fluidity Cl- Na+ H2O mucus 1 2 3 X apical membrane The CFTR protein cannot block the sodium channels so they are always open CFTR non- functional Water drawn out by osmosis Na+ channel open H2O basal membrane tissue fluid H2O Cl-

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