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25 Cards in this Set
- Front
- Back
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What do the dietary carbohydrates include?
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1. Starch (amylose & amylopectin)
2. Glycogen 3. Isomaltose 4. Maltose 5. Lactose 6. Sucrose 7. Cellulose |
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Which starch is not digested and why?
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Cellulose
Because it contains Beta-1,4 glycosidic bonds |
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Why are all other carbohydrates able to be digested (except cellulose)?
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They contain alpha-1,4 and alpha-1,6 glycosidic bonds
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Where does carbohydrate digestion begin?
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alpha-amylase (ptaylin) in the mouth
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What does alpha amylase (ptaylin) break down?
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Oligosaccharides into disaccharides
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What happens to carbohydrate digestion in the stomach?
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It stops because the low pH inactivates the alpha-amylase
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What causes carbohydrate digestion to continue in the duodenum?
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Pancreatic alpha-amylase
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What are the disaccharides that pancreatic alpha-amylase produces?
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Maltose (glucose-glucose)
Sucrose (glucose-fructose) Lactose (glucose-galactose) |
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Can disaccharides be absorbed into the luminal membranes of the enterocytes?
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no they have to be broken down into their respective monosaccharides
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What are the enzymes that break down the disaccharides at the luminal membrane of the enterocyte?
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Glucoamylase (maltase)
Lactase Sucrase |
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How are glucose and galactose moved across the enterocyte cell membrane?
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Sodium dependent transporters
Insulin independent glucose transporters |
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Why can hexoses be transported across the abluminal membrane of the enterocyte and into the hepatic portal circulation?
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They are hydrophilic so they don't need transporters
a hexose is a monosaccharide with six carbon atoms |
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What is secreted in the stomach, pancreas and small intestine that digest protein?
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Proteases
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What does the low pH of the stomach do to proteins?
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Low pH denatures proteins
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What does pepsin do?
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Pepsin primarily produces shorter chain polypeptides and some amino acids
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What is an acid-stable endopeptidase?
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Pepsin
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How is pepsin acivated?
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By low pH or the activity of other pepsin molecules
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What are the inactive proteolytic precursors that are secreted by the pancreas?
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Trypsinogen
Chymotrypsinogen Procarboxypeptides Proelastase |
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How are the zymogens activated?
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Enterokinase converts trypsinogen to trypsin and that activates everything else
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What proteolytic enzyme is produced by the enterocytes themselves?
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Aminopeptidase (clips off single amino acid from N-terminus of oligopeptides)
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What chops up the shorter length polypeptides & oligopeptides (short chains)?
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Trypsin
Chymotrypsin Carboxypeptidase Elastase |
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What yields dipeptides?
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Aminopeptidase
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How are amino acids & dipeptides transported into the enterocyte?
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Sodium dependent amino acid transporters
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What protein derivatives are transported across the abluminal membrane and into the hepatic portal circulation?
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amino acids
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What happens to dipeptides once they enter the enterocyte?
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They are further broken into single amino acids by intracellular peptidases
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