1. What is the effect in each case? (a) injection of secretin and CCK (b) inject

Question

1. What is the effect in each case? (a) injection of secretin and CCK (b) injection of gastrin (c) ingestion of caffeine (d) injection of PTH 2. You take a drug that blocks the active transport of sodium out o What result(s) would you expect? Explain. of sodium out of the GI tract. 3. People with lactose intolerance can successfully eat ice cream other lactose- re ingesting the food, e a tablet ctaining lactase enzymes immediately (a) If a lactose intolerant person takes a lactase tablet, how does carbohy digestion differ in their GI tract compared with a non-lactose in person? (b) Will these lactase tablets help a person if they are sucrose intolerant? 4. You are able to obtain the following from the human digestive system: saliva secretions of the stomach enzymes found in the small intestine What would each of the above do to: (a) starch (b) water (c) lactose (d) proteins One hour later, you add starch to the tube. What will be present in your tube after another hour has passed? 5. You put a solution of salivary amylase into a tube. You add trypsin to the tube. 6. You have a five test tubes. These tubes (#1-45) contain solutions of substances as specified below. Describe what would be in each of these tubes after any enzyme reaction(s) go to completion: Tube # 1: lactose, lactase, maltose, maltase, sucrose Tube #2: sucrose, galactose, starch, amylase, dextrinase, and glucoamylase Tube #3: triglycerides, bile salts, pancreatic lipase, sucrose, sucrase Tube #4: pepsinogen, myosin, HCl Tube #5: pepsinogen, myosin

Explanation / Answer

1. a. Cholecystokinin (CCK) is the hormone responsible for delivering pancreatic enzymes and bile into small intestine. It causes release of digestive enzymes from pancreas into duodenum and contracts the gall bladder to release bile into duodenum. This action will aid digestion and reabsorption of molecules that stimulate CCK secretion. Hence, further release of CCK will be inhibited. CCK also controls food intake by the ventricles of the brain. Its injection will induces lack of hunger in animals.

Secretin, on the other hand, will regulate water homeostasis in the body. It is a peptide hormone that is secreted by the S cells of the duodenum. It regulates the pH of the duodenum by inhibiting secretion of gastric acid by the parietal cells of the stomach and stimulates secretion of bicarbonate in the pancreas. Hence, digestive enzymes in the duodenum will function optimally.

Injection of secretin and CCK will improved digestion of food by increased delivery of pancreatic enzymes and bile to duodenum and balancing the pH to optimal function of these enzymes.

b. Gastrin is a peptide hormone that stimulates gastric acid/hydrochloric acid by the parietal cells of the stomach via histamine-2 receptor. Hence, it will aid in gastric motility. It is secreted by the walls of the pyloric end of the stomach, where the stomach attaches to duodenum. It promotes the growth of gastric mucosa.

c. Caffeine is a stimulator of the central nervous system that antagonizes levels of adenosine receptors. Injection of caffeine will stimulate energy metabolism in the brain. However, it will also prevent blood flow to the brain, as it is a vasoconstrictor. It also acts by inhibiting of phosphodiesterase and the release of calcium from intracellular stores. Further, it antagonises benzodiazepine receptors in brain. Injection of caffeine causes increased energy, increased heart rate, insomnia and restlessness.

d. Parathyroid hormone is a hormone secreted by the parathyroid gland. It increases renal calcium absorption in the ascending loop of Henle, distal tubule, and collecting tubule and inhibits phosphate reabsorption by proximal tubules. When PTH binds to receptors on osteocytes in bone, the calcium ions are pumped from the bone fluid into the extracellular fluid. PTH converts 25-hydroxyvitamin D to 1, 25-dihydroxyvitamin D-3 [1,25-(OH)2 D3], by activating 1-hydroxylase in the proximal tubules of the kidney.

2. The sodium transport system in GI tract is linked to glucose uptake. Sodium (3 ions) is transported out of the cell and glucose (2 molecules) is transported into the cell. If sodium transport out of the cell is inhibited, glucose transport will also be inhibited, since sodium transport supplies the energy for the glucose transport.

3. a. Lactose intolerance is caused by the deficiency of lactase in the intestine. Hence, lactose cannot be broken down to glucose and galactose and lactose will be absorbed by the intestine.

In a normal non-lactose intolerant individual, lactase will completely break down to glucose and galactose. Glucose is reabsorbed in small intestine and is used in glycolysis.

Lactase enzyme when fed to a lactose intolerant individual, will cause breakdown of lactose to glucose and galactose. However, the lactase will not completely breakdown the lactose. Some lactose will still remain that may case intestinal problems of diarrhea. Such individuals should take lactase with milk with reduce lactose content (Skimmed milk).

b. Lactase will only break down lactose as it breaks beta 1,4 glycosidic bond. It has no effect of sucrose, which has alpha 1,2 glycosidic bonds. Hence, sucrose intolerant individuals will not benefit from consuming lactase.

As per Chegg’s rules, only one question needs to be answered.

  

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