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20 Cards in this Set
- Front
- Back
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What are the 3 main consumed carbohydrate sugars?
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Sucrose (disaccharide, cane sugar), lactose (dissacharide, milk sugar), starches
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How are carbs digested in the mouth?
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ptaylin (alpha amylase) hydrolyzes starch into maltose (glu glu)and other short polymers.
Alpha amylase is inhibited by acid (stomach). Only 5% of the carbs are hydrolyzed in the mouth, but amylase continues to work in the esophagus in the bolus. |
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How are proteins digested in the stomach?
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Pepsin works on collagen in meat. Pepsin initiates protein digestion to produce proteoses, peptones, polypeptides.
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How are carbs digested in the SI?
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Pancreatic amylase breaks down all starches into maltose. Intestinal epithelial brush border enzymes contain the disaccharidases (lactase, sucrase,
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Describe digestion of proteins by secretion of enzymes in the SI? Then describe by brush border enzymes?
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First trypsin, chymotrypsin cleave to polypeptides. Carboxypeptidases only gives you a few AAs free at the end, Proelastase digests elastin fibers. MOST PROTEINS REMAIN POLYPEPTIDE at this stage.
The brush borders have aminopolypeptidases and dipeptidases that split proteins into 1,2, or 3 length AAs. these are uptaken by enterocytes. The 2, 3 length AAs are cleaved to single ones as soon as they enter the blood. |
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Why not just absorb the whole protein intact?
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Immunological reasons.
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What are the various forms of ingested fat that our body digests?
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Triglycerides
Cholesterol esters Phospholipids |
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How are fats digested in the mouth?
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There is some lingual lipase that does minimal digestion.
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What enzymes act on fats in the small intestine?
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Pancreatic lipase (most powerful)
Enteric lipase (not very significant) |
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When triacylglycerol is digested in small intestine, what is produced?
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2-monoglycerol
2 free fatty acids. |
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How does the body prevent ressembly of triacylglycerol once it is hydrolyzed?
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Bile salts form micelles around the MAG and FA, preventing reaggregation and allowing its absorption by intestinal cells.
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How is cholesterol ester/phospholipid digested?
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Most cholesterol is in the form of cholesterol ester (cholesterol linked to ester). These are hydrolyzed off by cholesterol ester hydrolase.
The phospholipid is hydrolyzed by phospholipase A2. |
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How do bile salts work?
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Bile salts and lecithin are emulsifiers of fats. Polar heads dissolve in water; non polar dissolve in fats. This eases emulsification into droplets, increasing the surface area and reducing the interfacial tension.Lipase then acts at the surface.
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How much fluid must be absorbed a day from the lumen of the GI tract.
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7-8 L in SI
1-2 L in LI |
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What kinds of substances can be absorbed in the stomach?
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Alcohol, Aspirin
Highly lipophilic |
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What is another name for the folds of Keckring? What do they do? Where are they found?
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The folds of Keckring are found in the SI mucosa and are also called valvulae connivents- these increase the surface area 3xs. They are especially concentrated in the duodenum and jejunum.
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What arrangement allows for lymph absorption in the GI tract?
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A central lacteal surrounded by a vascular network.
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What role does pinocytosis play in absorption?
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A small one- some substances are absorbed like by this method
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What protein allows microvilli to move
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actin
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What are 3 mechanisms of absorption?
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Diffusion
Active transport solvent drag |
