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21 Cards in this Set
- Front
- Back
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1. What are the major dietary carbohydrates?
What are the major products of digestion of carbohydrates? |
1. Starch
2. Sucrose 3. Lactose 4. Indigestible fiber 1. Glucose 2. Galactose 3. Fructose |
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2. What is glucose converted to when it enters the cell?
What can happen to this compound? |
Glucose 6-phosphate
1. Glycolysis (produce pyruvate) 2. Glucose 1-P to UDP for synthesis of glycogen or proteoglycan compounds 3. Enter pentose phosphate pathway (produce NADPH) |
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3. What happens to galactose and fructose?
What is the major storage form of glucose? Where are the largest stores? |
Converted to intermediates in pathways by which glucose is metabolized
Glycogen Muscles and liver |
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4. What are the current dietary recommendations for carbohydrates?
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Minimum: 25% of total calories
-maintain brain function Total: 55% - 75% of total calories -reduce risk of major chronic diseases Sugars: <10% of total calories |
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5. What is the basic structure of the dietary carbohydrates?
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1. Lactose: glucose and galactose
2. Sucrose: glucose and fructose 3. Starches -amylose: pure glucose -amylopecton: glucose but branches every so often |
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6. How do the monosaccharides differ in structure?
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Glucose and Galactose
-differ on 4' C in orientation of OH group Fructose -pentomer (5 C in ring) |
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7. What type of bond joins the monosaccharides in lactose and sucrose?
How are these bonds denoted? |
Glycosidic bond
β - "up" (lactose) α - "down" (sucrose) |
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8. Which enzyme digests lactose?
Where does the enzyme digest? |
Lactase
Specific for β 1,4 linkage between glucose and galactose |
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9. What is the structural foundation for plaque?
What is the structure of this? |
Dextran
Glucose polymer with main linkage of α-1,6 BUT also has α-1,3 branch linkages |
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10. How is dextran formed?
What enzyme is needed? From where is this enzyme obtained? |
Glucosyl units from sucrose are transferred to form glucose polymer
Dextran-sucrase (glucosyltransferase) Streptococcus mutan |
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11. Why is dextran not digestable by salivary α-amylase?
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B/c there is an α-1,6 linkage
An enzyme in the intestine digests this type of linkage |
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12. Which enzyme digest starch?
Where does this digestion occur? Which enzyme plays a greater role in starch digestion? |
Salivary and pancreatic α-amylase
Breaks α-1,4 linkage between glucosyl residues at random points w/in starch Pancreatic amylase >> salivary amylase |
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13. What are the two disaccharide products of starch digestion?
What happens to them? |
Maltose and Isomaltose
Digested by disaccharidases on lumenal surface of intestinal microvilli |
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14. What enzyme digests sucrose?
Where does it cleave bonds |
Sucrase
α-1,2 linkage between glucose and fructose |
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15. Where are the enzymes that digest sucrose and lactose located?
What is partially digested in the mouth? What are the products of starch? |
In intesitne
Starches (by salivary α-amylase) α-dextrins |
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16. Why does the digestion of starch stop in the stomach?
What does the stomach release to neutralize the stomach acid? What happens in the lumen of the gut (active site)? |
Salivary amylase is destroyed by stomach acids
Bicarbonate (HCO3- as well as pancreatic α-amylase) Digestion of disaccharides to monosaccharides that are taken up by intestinal epithelial cells |
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17. What does lactose intolerance cause?
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1. Diarrhea
-lactic acid produced by anaerobic bacteria draws water by osmosis into intestinal lumen 2. Gas -bacterial fermentation produces H and methane gase |
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18. What carbohydrate in insoluble and why?
What can fibers in fruits and vegetables protect against? |
Cellulose b/c humans do not have enzyme to cleave β-1,4 linked glucose
Heart disease, obesity, diabetes, and possibly colon cancer |
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19. What does facilitative transport carrier in/out of cells?
How does facilitative transport work? In what type of cells does it occur? |
Glucose, fructose, and galactose
Facilitative transport carriers move down a concentration gradients Occurs in all cells **Facilitative transporters are reversible |
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20. What is the other type of glucose transport?
Where does this occur? What does this required? |
Secondary active transport
Epithelial cells of the intestine and kidney Na+ |
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21. How does secondary active transport of glucose work?
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Na+, K+ -ATPase in basolateral membrane pump Na+ against concentration gradient into extracellular fluid
Glucose consequently moves against its concentration gradient from low concentration in lumen to higher concentration in cell by traveling on same carrier as Na+ |
