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GIR Test 1 > B5-096 GI Physiology III > Flashcards

B5-096 GI Physiology III Flashcards

1
Q

what phase of digestion has a large secretion of insulin?

A

cephalic phase

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2
Q

where are carbohydrates and lipids absorbed?

A

duodenum > jejunum > ileum

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3
Q

where is iron absorbed?

A

duodenum

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4
Q

where is folate absorbed?

A

duodenum

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5
Q

where is calcium absorbed?

A

primarily duodenum but jejunum and ileum as well

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6
Q

where are bile acids absorbed?

A

iluem > jejunum, colon > duodenum

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7
Q

where is cobalamin absorbed?

A

ileum

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8
Q

breaks down carbohydrates at the a 1-4 linkages

A

a-amylase

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9
Q

can a-amlyase split a1-6 linkages?

A

no

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10
Q

continued breakdown of carbohydrates after a-amylase is carried out by enzymes at the

A

brush border

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11
Q

coupled transporter that brings Na+ and glucose into cell

A

SGLT-1

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12
Q

mediates facilitated diffusion of fructose into cell

A

GLUT5

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13
Q

mediates monosaccharide efflux into interstial space

A

GLUT2

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14
Q

lactase splits […]
both monomers are transported via […]

A

lactose
SGLT-1

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15
Q
  • two enzymes
  • sucrase moiety splits sucrose/maltose
  • isolmaltase activity splits a-limit dextrins/maltose
A

sucrase-isomaltase

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16
Q

removes glucose monomers for transport

A

glucoamylase

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17
Q

what do brush border peptidases do?

A

progressively hydrolyze oligopeptides to amino acids

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18
Q

H/oligopeptide cotransporter

A

PepT1

there is also a Na/AA cotransporter

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19
Q

the enterocyte can directly absorbs some oligopeptides through […]

these are then disgested to amino acids by […] within the cytoplasm

transporter/ enzyme

A

PEPT1

peptidases

there is also a Na/AA cotransporter

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20
Q

enterocytes take up 90% of protein resulting in […]

A

complete lysosomal degradation

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21
Q

M cells take up 10% of protein but half […]

A

emerges from the membrane intact

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22
Q

package proteins and present them to APCs in interstitium

A

M cells

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23
Q

endopeptidases

3

A
  • trypsin
  • chymotrypsin
  • elastase
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24
Q

exopeptidases

2

A

carboxypeptidases A and B

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25
Q

result in oligopeptides (2-6 AA)

endo or exopeptidases

A

endopeptidases

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26
Q

result in single amino acids

endo or exo peptidases

A

exopeptidase

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27
Q

produce peptide with C terminal basic AA

A

trypsin

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28
Q

produce peptide with C terminal neutral AA

2

A

chymotrypsin
elastase

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29
Q

what is the advantage of oligopeptide absorption?

think about PepT1

A

PepT1 moves several AA per turnover = faster absorption

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30
Q

act within the AA chain

endo or exo peptidases

A

endopeptidase

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31
Q

act on either end of the AA chain

endo or exopeptidases

A

exopeptidases

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32
Q

hydrolyze TAGs at surface

TAGs from core replace them, causing droplet to shrink

A

pancreatic lipase

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33
Q

describe the breakdown of emulsion droplets to mixed micelles

A
  1. emulsion droplet: pancreatic lipase breaks down TAGs to shrink core
  2. multilamellar liquid-crystalline: bile salts cause small pieces to bud off into multilamellar vesicle
  3. unilamellar vesicle- formed by addition of more bile salts to multilamellar vesicle
  4. mixed micelle: even more bile salts
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34
Q

how to lipids enter enterocytes?

3 ways

A

mixed micelle crossed into acidic microenviornment to release lipids:
* non ionic diffusion
* incorporation into enterocyte membrane
* carrier-mediated transport

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35
Q

why do the lipids release when the mixed micelle crosses into the acidic microenvironment?

A

protanation of FFA is favored in the acidic environment

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36
Q

FAT/CD36 does what?

A

carrier mediated transport of lipids into enterocytes

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37
Q

enterocytes can reform esters to make

A

apoliproteins and chylomicrons

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38
Q

describe the re-esterfication of lipids into chylomicrons and VLDLs

A
  1. LCFA are coverted back to lipids in SER
  2. fat droplets form in cisternae of SER
  3. apoliproteins are synthesized in the RER and move to SER to associate with droplets (except Apoli A-1)
  4. chylomicrons and VLDLs arrive at cis face of Golgi to be glycosylated
  5. vesicles carrying VLDLs bud off trans-Golgi and move to membrane
  6. vesicle fuse to membrane to be released
  7. chylomicrons and VLDLs enter lymph
  8. enter circulation

Apoli A-1 associated with chylomicrons in Golgi

39
Q

fatty acids most readily available to us after eating

A

short and medium chain

40
Q

produce VLDLs and chylomicrons

A

enterocytes

41
Q

after being synthesized in the RER, apoliprotein A moves to

A

Golgi to associate with chylomicrons

42
Q

3 parts of folate

A

pteridine moiety (biologically active)
p-aminobenzoate
glutamate

dietary folate just has more gluatmates

43
Q

for folate breakdown, brush border peptidases remove

A

all but one glutamate

becomes PteGlu1

44
Q

brings PteGlu1 into enterocyte

broken down folate

A

folate-OH exchanger

45
Q

critical to serve as methyl donor for DNA synthesis or methionine synthesis

A

folate

THF is methylated

46
Q

describe the absorption of cobalamin

A
  1. cobalamin bound to nutrients in food
  2. gastric acid/pepsin release cobalamin from dietary protein
  3. gastric glands secreted haptocorrin which binds to cobalamin
  4. gastric parietal cells secrete intrinsic factor
  5. pancreas secretes proteases and HCO3-
  6. cobalamin is released after degradation of haptocorrin (duodenum)
  7. IF-CBL complex forms
  8. ileal enterocyte absorbs IF-CBL complex
47
Q

[…] binds cobalamin in somach

A

haptocorrin

48
Q

binds cobalamin in duodenum

A

intrinsic factor

49
Q

the IF-CBL complex is absorbed in the

A

ileus

50
Q

to efflux cobalamin out of enterocyte into interstitial space, it must bind to

A

trans-cobalamin II

51
Q

describe active Ca++ absorption

A
  1. Ca++ enters via channel
  2. binds cytoplasmic calbindin or goes into intracellular organelles
  3. effluxed into interstitial space via Na/Ca exhanger
52
Q

where does active Ca++ uptake occur

A

duodenum

53
Q

predominant paracellular absorption of Ca++ throughout small intestine

A

passive

54
Q

active form of vitamin D drives the production of

A

calbindin

55
Q

describe the absoprtion of non-heme iron

A
  1. Dcytb reduces non-heme iron Fe3+ to Fe2+
  2. DMT cotransports Fe2+ with H+
  3. Fe2+ transfers to mobilferrin
  4. Fe2+ leaves cell via ferroportin and hephaestin oxidizes it to Fe3+
  5. iron binds to transferrin in plasma
56
Q

heme iron absorbs at [..] the rate of nonheme iron

A

10x

57
Q

why does hephaestin oxidize Fe2+ to Fe3+ ?

A
  • keeps it in interstitial space
  • allows to bind to transferrin
58
Q

describe the absoprtion of heme iron in the duodenum

A
  1. Heme Fe2+ enters cell (unknown mechanism)
  2. Fe2+ transfers to mobilferrin
  3. Fe2+ leaves cell via ferroportin and hephaestin oxidizes it to Fe3+
  4. iron binds to transferrin in plasma
59
Q

short chain and medium chain lipids directly enter

A

systemic circulation

60
Q

which zone of the liver has highest oxygen tension?

A

zone 1

61
Q

what zone of the liver do beta oxidation and gluconeogenesis occur in?

A

zone 1

high oxygen demand, greatest area of oxygen

62
Q

what zone of the liver do lipogenesis, ketogenesis, tryglyceride synthesis and glycolysis occur in?

A

zone 3

63
Q

describe the synthesis of bile acid through CYP7A1

A

cholic acid -> deoxycolic acid -> glycine

64
Q

cholic acid, deoxycholic acid, and glycine are products of which CYP route?

bile acid synthesis

A

CYP7A1

65
Q

describe bile synthesis through the CYP27A1 route

A

chenodeoxycholic acid -> lithocolic acid -> taurine

66
Q

chenodeoxycholic acid, lithocolic acid, and taurine are products of which CYP route?

bile acid synthesis

A

CYP27A1

67
Q
  • bile duct epithelial cells
  • protect hepatocytes by transporting bile
A

cholangiocytes

68
Q

what conjugates bile salts to bile acids?

A

bacteria

69
Q

how much bile acids are reabsorbed?

A

90-95%

70
Q

feedback to liver to prevent production of primary bile acids

2

A

FGF19
recycled bile acids

71
Q

the production of amino acids produces […] which has to be gotten rid of

A

ammonia

72
Q

85% of the circulating […] is taken up by the liver and processed to urea

A

ammonia

73
Q

urea is excreted through to kidneys or […] into the colon

A

recycled

74
Q

deamination of hepatic amino acids results in

2

A

glutamate and keto acid

amino group is transferred to alpha-ketoglutarate

75
Q

the NH4+ that results from the regeneration of alpha-ketoglutarate is consumed in the

A

urea cycle

76
Q

ApoB-48

A

chylomicrons

exogenous lipids to liver

77
Q

B100

A

VLDL

78
Q

rate limiting step of cholesterol synthesis

A

HMG CoA reductase

79
Q

why is cholesterol synthesis tightly regulated?

A

very energy expensive

80
Q

only two ways to get rid of cholesterol

A
  • secreted in bile acids
  • secreted directly into bile duct -> feces
81
Q

what can the liver do with cholesterol?

3

A
  • excrete in bile
  • excrete in feces
  • package to VLDLs
82
Q

moves peptides into intestinal epithelial cells together with a proton supplied by Na/K/H+ exchanger

A

PEPT1

83
Q

receptors for B12 are in the […]

A

terminal ileum

84
Q

intrinsic factor is made by

A

parietal cells

85
Q

moves vitamin B12 into blood

A

transcobalamin II

86
Q

individuals who avoid meat/dairy intake have low levels of what vitamin?

A

B12

87
Q

non-heme iron transporter

A

DMT1

88
Q

functions to remove iron from heme

A

heme oxygenase

89
Q

transports iron out of enterocyte

A

ferroportin

90
Q

Roux-en-Y causes thaimine deficiency via

A

diversion of chyme from duodenum to jejunum

91
Q

can cause thiamine deficiency

3

A
  • Roux-en-Y
  • excessive alcohol consumption
  • excessive vomiting (especially in pregnancy)
92
Q

cause a reduction in the sequential breakdown of emulsion droplets

A

bile acid sequestrants

93
Q

increase bile acid synthesis in liver and do not decrease bile production

drug class

A

bile acid sequestrants

94
Q

a decrease in vitamin D results in a decrease of

A

calbindin

GIR Test 1 (16 decks)

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