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21 Cards in this Set
- Front
- Back
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How are carbohydrates digested generally?
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by hydrolysis to form oligosaccharides, then free mono and disaccharides.
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What is known as the increase in blood glucose after a test dose of a carbohydrate compared with that after an equivalent amount of glucose (as glucose or from a reference starchy food)?
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glycemic index
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Which sugars have a glycemic index of 1 (or 100%)?
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On hydrolysis lactose, maltose, isomaltose, and trehalose give rise to glucose and galactose. So they have a glycemic index of 1
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Which sugars are absorbed less rapidly and have a lower glycemic index?
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Fructose, sugar alcohols, and sucrose
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T/F: the glycemic index of starch varies from 0 to 1.
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True
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Why are foods that have a low glycemic index considered to be healthier?
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They cause less fluctuation in insulin secretion.
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Why do resistant starches and nonstarch polysaccharides cause gas?
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they provide substrates for bacterial fermentation in the large intestine.
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What else do bacteria use from the nonstarch polysaccharides?
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butyrate and other short chain fatty acids for energy.
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The hydrolysis of starch is catalyzed by which enzymes?
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Salivary and pancreatic amylases.
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Which bonds do amylases hydrolyze?
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they catalyze random hydrolysis of alpha (1-4) glycoside bonds, yielding dextrins then a mixture of glucose, maltose, and maltotriose.
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Where are disaccharidases found in the gut?
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within the brush border
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What can cause failure to thrive in infants when they are fed on breast milk or normal infant formula?
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congenital deficiency of lactase
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What enzyme is occasionally deficient among the Inuit, leading to sucrose intolerance with persistent diarrhea and failure to thrive when the diet contains sucrose?
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Sucrase-isomaltase
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What is the transport protein that absorbs both glucose and galactose via a Na+ dependent process in the SI?
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SGLT 1
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T/F: glucose and galactose compete for binding to SGLT 1.
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True
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T/F: other monosaccharides are absorbed by carrier-mediated diffusion.
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True
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What happens when there is a moderately high intake of fructose or sugar alcohols?
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Some may remain in the lumen and get passed onto the LI where enterocytes ferment it.
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What could occur with large intakes of fructose and sugar alcohols?
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Osmotic diarrhea. (lots of fructose still in the lumen can cause water to follow it, leading to watery stool)
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SGLT 1 transporter is coupled to what pump, allowing glucose and galactose to be pumped against their gradients?
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Na+/K+ pump
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Which GLUT allows fructose as well as glucose and galactose to be transported down their concentration gradients?
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GLUT 5 Na+ independent facilitative transporter
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Which GLUT allows all sugars to exit cells?
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GLUT 2
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