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DEMS unit 1 > Digestion/Absorption > Flashcards

Digestion/Absorption Flashcards

1
Q

Drug inhibiting lipase

A

Olestra

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2
Q

fat soluble vitamins

A

A, E, D,K

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3
Q

water soluble vitamins

A

biotin, folic acid (simple diffusion), vitamin B12 (specific transporter)

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4
Q

channel critical for absorption

A

Na/K ATPase pump

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5
Q

water absorption linked to what?

A

Na absorption

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6
Q

channels for Na absorption

A

Na/glucose & galactose or Na/amino acid cotransport, NaCl cotransport, Na/H exchange, passive diffusion

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7
Q

Chloride absorption

A

passive in proximal intestines, more in distal ileum/colon due to less leaky TJs; Cl exchanged for HCO3 of setting acids from bacteria

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8
Q

K absorption: active or passive?

A

passive

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9
Q

Potassium absorption

A

paracellular movement in jejunum; transcellular incolon

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10
Q

Ca absorption

A

Ca and Mg compete for uptake

- Ca enters enterocyte passively down electrochemical gradient in proximal intestines-Ca ATPase pumps Ca out into blood

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11
Q

Vitamin D

A

synthesized in skin/absorbed by intestine

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12
Q

where is vitamin D is vitamin D metabolism

A
  • vitamin D is 25-hydroxylated in liver
  • 25-OH Vit D is 1-hydroxylated in kidney in presence of parathyroid hormone
  • Vit D binds to cytoplasmic receptor, activating transcription/translation
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13
Q

how does vitamin D relate to Ca

A

vitamin D stimulates uptake of Ca by increasing Ca binding proteins and Ca ATPase molecules

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14
Q

Where is iron absorbed?

A

regulated absorption in proximal intestines

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15
Q

fates of Fe

A

-transported across apical membrane as heme or Fe (receptor mediated)
THEN
- binds to apoferritin to form ferritin – stays in cell and lost when cell dies
OR
- binds to transferrin (carrier protein), leaves the cell adn goes into blood

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16
Q

trend of water permeability through intestines

A

paracellular water permeability decreases from proximal to distal in the small intestines
- lowest in colon since trying to solidify waste and needs to link water movement to transcellular ion movement

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17
Q

Osmotic diarrhea causes

A

(due to impaired digestions/defects in absorption)

  • lactase deficiency
  • ileal resection – bile salts not absorbed
  • Celiac disease
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18
Q

Celiac disease

A
  • Sprue; genetic

- with gluten sensitivity –> gliaden-induced destruction of villi

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19
Q

Vibrio cholerae causes what kind of diarrhea

A

Secretory diarrhea– increases cAMP levels in cells and in turn activates CF chloride channel (and thus water) on the luminal surface
- also have paracellular movement of Na into lumen and thus water as well

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20
Q

Oral rehydration therapy

A

antibiotics plus KHCO3 to prevent hypokalemia and metabolic acidosis, glucose (or amino acids) with NaCl to facilitate absorption of electrolytes and water

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21
Q

biggest risk factor for dehydration

A

hypokalemia

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22
Q

Amylase

A

secreted by salivary glands into mouth/stomach; digests starch to create polysaccharides

  • also secreted by pancras into duodenum/jejunum to digest starch into polysaccharides
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23
Q

lingual lipase

A

secreted by serous glands of tongue

  • digests fat into monoglycerides and fatty acids
  • present in mouth ant stomach
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24
Q

pepsin

A
  • secreted by stomach

- digests proteins into polypeptides

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25
Q

Trypsn

A

secreted by pancreas into duodenum/jejunum to breakdown protein/polypeptides into small peptides and amino acids

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26
Q

chymortypsin

A

secreted by pancreas into duodenum/jejunum to break down proteins/polypeptides into small peptides and amino acids

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27
Q

elastase

A

secreted by pancreas into duodenum/jejunum to break down proteins/polypeptides into small peptides and amino acids

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28
Q

carboxypeptidases

A

secreted by pancreas into duodenum/jejunum to break down proteins/polypeptides into small peptides and amino acids

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29
Q

lipase and colipase

A

secreted by pancreas into duodenum/jejunum to digest fat into monoclycerides, fatty acids, and cholesterol

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30
Q

Phospholiase A2

A

secreted by pancreas into duodenum/jejunum to digest fat into monoclycerides, fatty acids, and cholesterol

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31
Q

Cholesterol ester hydrolase (non-specific lipase)

A

secreted by pancreas into duodenum/jejunum to digest fat into monoclycerides, fatty acids, and cholesterol

32
Q

Bile salts

A

secreted by liver into duodenum/jejunum to emulsify and dissolve fats

33
Q

HCL

A

secreted by stomach to kill bacteria and denature proteins

34
Q

NaHCO3

A

ubiquitous; buffers pH

35
Q

Mucus

A

ubiquitous; lubrication, protection of mucosal surfaces

36
Q

pepsinogen

A

zymogen released by chief cells into stomach; converted to active pepsin by stomach acid

37
Q

typsinogen

A

secreted into duodenum and activated to trypsin by enterokinase

38
Q

largest source of starch in most human diets

A

amylopectin (plant starch) containing alpha 1,4, and alpha 1,6 linkages

39
Q

cellulose

A

polymer linked by beta 1,4 linkage that can’t be digested by intestinal enzymes; major component of dietary fiber

40
Q

amylase digestion

A

catalyzes internal alpha 1,4, bonds to generate maltose, and maltotriose and alpha-limit dextrin

  • never glucose as product
41
Q

2 types of glucose polymers in diet

A

amylose, amylopectin

42
Q

role o fenzymes in brush border

A

convert small polysaccharides to sugar monomers

43
Q

surase-isomaltase (SI)

A

breaks down 1,6 linkages of alpha-limit dextrin to glucose

44
Q

maltase-glucoamylase (MGA)

A

breaks down maltriose to glucose

45
Q

lactase

A

breaks down lactose to glucose

46
Q

sucrase

A

breaks down sucrose to glucose

47
Q

how to transport sugars into cells

A

intestinal sugar transporters

  • Na-dependent glucose transport (SGLT1)
  • Na-independent fructose transporter (GLUT5; GLUT2)
48
Q

Na - dependent glucose transporter

A

(SGLT1)located on apical side of enterocytes and transports glucose, galactose, and Na from intestinal lumen to cytosol

49
Q

Na-independentfructose transporter

A

(GLUT5 and GLUT2)

  • GLUT5 = apical; transports fructose form luemnt to cytosol
  • GLUT2 basolateral and transports all 3 monosaccharides (fructose, glucose, galactose) from cytosol to blood
50
Q

lactose intolerance

A
  • lactase absent from brush border
  • unabsorbed lactose draws water into intestinal lumen – osmotic diarrhea
  • gut bacteria metabolize lactose to form gases
51
Q

Absent SGLT1

A

Na/Glucose cotransporter; absence auses malabsorption fo glucose/galactose

  • diarrhea when ingesting dietary sugars due to reduced SI absorption fo Na and fluid; also fluid secretion due to osmotic effects of non-absorbed monosaccharide
  • potentially fatal neonatal condition of glucose-galactose malabsorption
52
Q

treat absent SGLT1 transporter

A

replace dietary glucose with frucose

53
Q

where is protein digestion

A

begins in stomach with pepsin; completed in SI with gastric, pancreatic, enterocyte brush-border and cytoplasmic peptidases

54
Q

2 classes of peptidases

A

endopeptidases and exopeptidases

55
Q

role of secreted endopeptidases

A

hydrolyze interior peptide bonds

56
Q

examples of endopeptidases

A

Pepsin (aromatic aa)
Trypsin - arginine/lysine
Chymotrypsin (aromatic aa)
Elastase (neutral aliphatic aa)

57
Q

secreted exopeptidase role/examples

A
  • hydrolyze one amino acid at a time from C-terminus of proteins/peptides
  • Carboxypeptidases A
  • Carboxypeptidases B
58
Q

brushborder proteases

A
  • aminopaptidase
  • Dipaptidyl aminopeptidasel
  • dipeptidase
59
Q

aminopeptidase

A

exoprotease at brush border removes one aa from N terminus at a time

60
Q

dipeptidyl aminopeptidase- removes

A

brush border enzyme; removes dipeptides from N terminus

61
Q

dipeptidase

A

brush border enzyme; converts dipeptides to amino acids

62
Q

amino acid absorption in intestine

A

via H dependent peptide transporter PEPT1

63
Q

fatty acid absorption

A

short chain fatty acidsdiffuse across apical memrane and re-esterified as triglycerides in smooth ER prior to uptake into chylomicrons that exocytose acros BL membrane

64
Q

when is pepsin active

A

below pH 5

65
Q

SI proteases

A

trypsinogen, chymotrypsinogen, pro-elastase, pro-carboxypeptidase A, pro-carboxypeptidase B

66
Q

Steps of Si protein digestion

A
  • Trypsinogen activated at brush border by enterokinase
  • trypsin activates all other precursors
  • trypsin, chymotrypsin, elastase, carboxypeptidase A and B hydrolyze protein to aa and di-tri- and oligopeptides
  • brush border proteases hydrolyze oligopeptides to amino acids
  • pancreatic proteases digest themselves and each other
67
Q

Protein absorption

A

by Na-dependent co-transport; di- and tripeptides absorbed (compared to only carbohydrate monomers)
- up to 70% protein absorbed this way

68
Q

specificities of 4 different amino acid carriers

A

neutral, basic, acidic, epcial one for proline/glycine

69
Q

what happens to protein inside enterocytes

A

di- and tripeptides hydrolyzed to amino acids by cytoplasmic proteins and exit BL membrane by facilitated diffusion to enter blood capillaries

70
Q

cysteinuria

A

genetic absence/defect of Na-amino acid transporters; same Na-amino acid transporter missing in kidneys

  • lack capacity for renal or intestinal absorption of cystine, lysine, arginine, and ornithine amino acids, so many excreted
  • renal defect – excreted amino acids in urine
71
Q

Hartnup disease

A

genetic absence/defect of neutral amino acid transporter

72
Q

Cystic fibrosis

A

genetic absence/defect of Cl channel called CFTR

73
Q

4 mechanisms of protein uptake

A
  • Active transport with Na (amino acids)
  • secondary active transport with Na (amino acids)
  • Secondary active transport with H (di/tripeptides)
  • Diffusion across basolateral side
74
Q

steps in triglyceride digestion

A
  • Fat droplets emulsified by bile salts and lecithin to form small particles and increase surface area for digestion
  • lipase and colipase digest triglycerides into 2-monoglyceride and 2 fatty acids that are then solubilized into bile-salt micelles to move to brush border –
  • monoglycerides and fatty acids dissociate and passively absorbed at brush border
75
Q

micelle

A
  • cylindrical structure with hydrophobic groups oriented interiorally and hydrophylic groups oriented towards aqueous phase
  • needed to transport products of fat digestion through water layer near surface of enterocytes
76
Q

What happens to fats after crossing apical membrane

A
  • monoglycerides and fatty acids cross apical membrane by passive diffusion
  • put into chylomicrons that travel to Golgi where they are incorporated into secretory vesicles
  • secretory vesicles travel to basolateral membrane where contents extruded into interstitial space and taken up into lacteals
77
Q

Fat malabsorption-associated disorders

A

Liver disease (can’t make micelles due to bile salt deficiency)

Pancreatic insufficiency (and CF) -lack enzymes to digest fat

weight loss meds - -inhibit lipase

DEMS unit 1 (15 decks)

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