Flashcard Set Preview
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| 1 |
What is the difference between the apical and basolateral surfaces of enterocytes?
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Apical: Faces lumen, has brush borderBasolateral: Does not face lumen, no brush border, has...
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| 2 |
What are the relative increases in surface area with each step of infolding?
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Pure cylinder: 3k cm2 (1x)Infolding: 10k (3x)Villi: 100k (30x)Microvilli: 2 M (600x)
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| 3 |
What is the average lifespan of enterocytes?How do they die?Where do they go when they die?What...
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2-5 daysApoptosis, but radiation can kill them tooSloughed off into lumen and out the back30g...
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| 4 |
What is the predominant pathway of calcium absorption?
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Absorption by diffusion in the small intestine through a paracellular pathway
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| 5 |
In the transcellular pathway of calcium absorption, how does calcium enter the cell?How does...
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Enters via Ca2+ channel on apical surfaceBound by calbindin, then released, then exits through...
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| 6 |
Where is 1,25-dhc (Vit. D metabolite) formed?What hormone regulates its formation?
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KidneyPTH
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| 7 |
What happens when Ca2+ absorption is too low?
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More PTH reaches the kidney-->More 1,25-dhc released by kidney-->binds to VDR (vitamin...
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| 8 |
Where is iron maximally absorbed?What transporter is used?
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DuodenumDCT-1 divalent cation transporter (aka DMT1), can also happen by diffusion
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| 9 |
Ferritin and transferrin bind which iron cation?Mobilferrin and IREG1 bind which iron cation?
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Fe3+ (ferric)Fe2+ (non-heme, ferrous)
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| 10 |
What are the 3 monosaccharides that can be absorbed by enterocytes?
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Glucose (hexose)Galactose (hexose)Fructose (pentose)
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| 11 |
How dose the SGLT-1 transporter work?
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It is a sodium/glucose (or galactose from lactose breakdown) transporterNa+ gradient is generated...
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| 12 |
How does fructose enter the enterocyte?How does it leave?How does glucose leave?
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GLUT-5GLUT-2 GLUT-2(all are facilitated diffusion)
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| 13 |
How do amino acids get into the enterocytes?Larger proteins (di, tri, tetrapeptides)?
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Na dependent, group specific membrane transportersH+/oligopeptide transporter (active process)
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| 14 |
What are two situations in which whole proteins are absorbed?
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Neonates (pinocytosis)Peyer's patches (lymphoid tissue) presenting protein to immunocompentent...
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| 15 |
What happens in Hartnup disease?
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Defect in System B (neutral AA) transporterNeutral AA's aren't absorbed well (e.g. phenylalanine)
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| 16 |
Trace a Fatty Acid from inside the enterocyte to systemic circulation
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Packed into chylomicrons (75-1200nm), excreted via basolateral membrane into lymph, reaches...
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| 17 |
What are the main differences between the SI and the LI in terms of water and electrolyte absorption?
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SI: absorbs more water, absorbs K+, secretes HCO3-LI: absorbs less water, secretes K+, absorbs...
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| 18 |
cAMP, cGMP, and Na+ serve as intracellular messengers to _____ NaCl absorption
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Reduce
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