7) In order to metabolize lactose, most infants express the enzyme lactase in their intestines. a. What kind of glycosidic linkage does lactose have? Please draw the individual monosaccharides to explain your answer. b. Please explain how the monosaccharides in lactose will be used in glycolysis. Be specific. c. How many pyruvate molecules and NADH molecules can be generated in glycolysis from one lactose molecule? Please explain. d. How many ATP molecules will be used and generated by 1 lactose molecule? Please explain.
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Infants express lactase in their intestines to metabolize lactose. a. How do the products of this reaction enter glycolysis (What are the sugars converted into for entry into glycolysis)? (0.5) b. How many pyruvate molecules can be generated from the metabolism of one molecule of lactose? (0.5) c. How many ATP molecules can be generated from lactose under aerobic and anaerobic conditions? (1)
Supreeta N.
2. Lactose is disaccharide sugar molecule which is the primary component inside the milk. Lactose intolerance is due to the disappearance after childhood of most or all of the lactase activity of the intestinal epithelial cells. Without intestinal lactase, lactose cannot be completely digested and absorbed in the small intestine and it passes into the large intestine, where bacteria convert it to toxic products that cause abdominal cramps and diarrhea. a. Draw the structure of lactose and name each individual sugar molecule. b. How does each of the monosaccharide from lactose enter the preparatory stage of glycolysis? (hint: use Figure 14-11 and 14-13 to figure out the pathway) c. What is malate-asparate shuttle? d. What is glycerol 3-phosphate shuttle? e. How many ATP can be generated if lactose is completely breakdown? Don't forget to account for ATP is used in activating the component of lactose before entering the glycolysis pathway. Assuming malate-asparate shuttle is used to transfer reducing equivalents into the mitochondria. Show your work! f. How many ATP can be generated if lactose is completely breakdown? Don't forget to account for ATP is used in activating the component of lactose before entering the glycolysis pathway. Assuming glycerol 3-phosphate shuttle is used to transfer reducing equivalents into the mitochondria. Show your work!
Adi S.
Lactose is a disaccharide sugar present in milk. Lactose is composed of two monosaccharides, galactose and glucose, that are joined together by a $\beta$ -glycosidic bond. The $\beta$ -glycosidic bond forms between the hydroxyl group on $C-1$ of galactose and C-4 of glucose. When lactose is digested, the glycosidic bond between galactose and glucose is hydrolyzed. The enzyme responsible for hydrolyzing lactose is lactase, which is found in the small intestine. Millions of people lack sufficient levels of lactase, and as a result, they experience lactose intolerance. If lactose is not hydrolyzed, it remains in the intestines. Bacteria in the gut ferment the lactose, causing many unpleasant symptoms such as indigestion, cramping, and gas. Fortunately, commercial preparations can enable lactoseintolerant individuals to consume and digest milk products without discomfort. Use the information provided to answer the following questions: a. Draw the structure of lactose. (The structures of galactose and glucose are shown on page 1037 with their carbon numbering scheme.) b. Lactase enzyme activity, like most enzymes, is sensitive to pH. Figure a $\Delta$ illustrates how lactase activity is affected by the pH of a solution. Based on the data in Figure a, what can you conclude about the $\mathrm{pH}$ of the small intestine? c. A glutamic acid in the active site of lactase is suspected to be involved in the catalytic mechanism. Draw the structure of the glutamicacid side chain in the ionization state that likely exists when lactase is most catalytically active.
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