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21-year-old student at a prestigious medical school. During the past 6 months, she experienced several bouts of severe abdominal bloating and cramps, followed by diarrhea. At first, she thought these episodes were caused by the stress of her demanding academic program. However, she noticed that the symptoms occurred approximately 1 hour after she drank milk or ate ice cream. On a visit home, Candice mentioned the symptoms to her mother, who exclaimed, "Don't you know that your father and I have never been able to drink milk?" Candice was examined by her primary care physician, who found her to be in excellent health. Because Candice's symptoms were temporally related to ingestion of dairy products, the physician ordered a lactose-H2 breath test, which confirmed that Candice has lactose intolerance. Her fecal osmolar gap was measured and was elevated. As a further confirmation of the diagnosis, Candice abstained from dairy products for 1 week and had no episodes of bloating, cramping, or diarrhea. Questions: 5. How are dietary carbohydrates digested in the gastrointestinal tract? What are the roles of salivary, pancreatic, and intestinal mucosal brush border enzymes in carbohydrate digestion? What three monosaccharides are the final products of these digestive steps? 8. How are dietary carbohydrates absorbed from the lumen of the gastrointestinal tract into the blood? Draw a small intestinal epithelial cell that shows the appropriate transporters in the apical and basolateral membranes. 9. Describe the steps involved in the digestion and absorption of lactose. 11. Propose a mechanism for Candice's lactose intolerance.

21-year-old student at a prestigious medical school.
During the past 6 months, she experienced several bouts of severe abdominal bloating and cramps, followed by diarrhea. At first, she thought these episodes were caused by the stress of her demanding academic program. However, she noticed that the symptoms occurred approximately 1 hour after she drank milk or ate ice cream. On a visit home, Candice mentioned the symptoms to her mother, who exclaimed, "Don't you know that your father and I have never been able to drink milk?" Candice was examined by her primary care physician, who found her to be in excellent health. Because Candice's symptoms were temporally related to ingestion of dairy products, the physician ordered a lactose-H2 breath test, which confirmed that Candice has lactose intolerance. Her fecal osmolar gap was measured and was elevated. As a further confirmation of the diagnosis, Candice abstained from dairy products for 1 week and had no episodes of bloating, cramping, or diarrhea.

Questions:
5. How are dietary carbohydrates digested in the gastrointestinal tract? What are the roles of salivary, pancreatic, and intestinal mucosal brush border enzymes in carbohydrate digestion? What three monosaccharides are the final products of these digestive steps?
8. How are dietary carbohydrates absorbed from the lumen of the gastrointestinal tract into the blood? Draw a small intestinal epithelial cell that shows the appropriate transporters in the apical and basolateral membranes.
9. Describe the steps involved in the digestion and absorption of lactose.
11. Propose a mechanism for Candice's lactose intolerance.

Added by Gabriel C.

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