new_n_lost
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A young boy presents with failure to thrive. Biochemical analysis of a duodenal aspirate after a meal reveals a deficiency of enteropeptidase (enterokinase).
The levels of which of the following digestive enzymes would be affected?
A. Amylase
B. Colipase
C. Lactase
D. Pepsin
E. Trypsin
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| mytime
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D.
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| usmle4me
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E
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| doc179
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E
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| Luckyall
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trypsin
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| keepgoing
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e
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| monam84
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E. trypsin is activated by enterokinase in duodenum, pepsin is activated in the stomach by acid H+
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| new_n_lost
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FORUM RULES-- Those who believe in telekinesis, raise my hand. I get enough exercise just by pushing my luck --P4U World.." The pure and simple truth is rarely pure and never simple."
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| new_n_lost
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The correct answer is E.
Enteropeptidase, formerly called enterokinase, activates trypsinogen by limited proteolytic digestion to give trypsin. Trypsin is itself capable of activating trypsinogen, which produces a positive feedback effect. Trypsin also activates chymotrypsinogen (and several other proteolytic enzymes), so deficiency of enteropeptidase results in a severe deficiency of enzymes that digest protein.
Amylase (choice A) aids in the breakdown of starches to oligosaccharides, maltose, and maltotriose.
Colipase (choice B), along with other lipases, functions to digest fats.
Lactase (choice C) is a brush-border disaccharidase that hydrolyzes the bond between galactose and glucose in lactose.
Pepsin (choice D) is a proteolytic enzyme secreted in an inactive form (pepsinogen) by the chief cells of the stomach. Pepsinogen is activated by stomach acid, and so is not dependent on enteropeptidase. Pepsin alone will not replace the activities of other proteolytic enzymes, partly because food does not remain in the stomach for an extended period of time.
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FORUM RULES-- Those who believe in telekinesis, raise my hand. I get enough exercise just by pushing my luck --P4U World.." The pure and simple truth is rarely pure and never simple."
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| lq2006
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E
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| dncosta
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E
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