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GEM > 3.01 GI Nutrtion > Flashcards

3.01 GI Nutrtion Flashcards

1
Q

What substance does not need digestion and is directly absorbed into intestinal lumen?

A

Glucose

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2
Q

Where does the greatest absorption of carbs, proteins, and lipids in small intestine take place?

A

Duodenum

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3
Q

Where is Ca+, Fe, and folate actively absorbed?

A

Duodenum

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4
Q

Where are bile acids absorbed in small intestine?

A

Throughout entire BUT ACTIVELY only at ILEUM*

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5
Q

Where is Vit B12 absorbed ?

A

Ileum

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6
Q

What carbs are dircetly absorbed by the small intestine?

A

Glucose, fructose, galactose (monosaccharides)

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7
Q

What initially breakdown carbohydrates aka starch?

A

A-amylase (acinar cells @ salivary glands + pancreas)

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8
Q

How are the initial oligosaccharides of amylose and amylopectin (starch) broken down?

A

A- amylase via intralumenal hydrolysis

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9
Q

What digests oligosaccharides further into monosaccharides?

A

Brush border disaccharidases

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10
Q

Where are the brush border dissachridases?

A

Integral membrane proteins of intestinal epithelial cells (apical side)

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11
Q

What are the oligosaccharidases?

A

Lactase
Glucoamylase (aka Maltase)
Sucrose-isomaltase

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12
Q

Lactase substrates and products?

A

Lactose —> glucose + galactose

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13
Q

Glucoamylase substrate and products?

A

Maltose —> glucose

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14
Q

Sucrase-isomaltase substrates and products?

A

Sucrose — > glucose + fructose

Maltose —> glucose

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15
Q

Na+ coupled transporter that mediates uptake of glucose or galactose from lumen on apical membrane?

A

SGLT1

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16
Q

What kind of transport is SGLT1?

A

Secondary active transport

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17
Q

Channel that mediates diffusion of fructose into enterocyte?

A

GLUT5

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18
Q

Channel that mediates facilitated diffusion of glucose, fructose, or galactose across BL membrane into interstitial space —> circulation?

A

GLUT2

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19
Q

Where are oligosaccharidases generally located in the GI tract/

A

Small intestine (should not be at the large intestine)

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20
Q

Lactase deficiency impacts what?

A

Glucose in plasma and H2 in breath

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21
Q

What will you notice in adults with a lactase deficiency?

A

Glucose levels should be normal but you will notice a higher than normal [H2 ]in their breath

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22
Q

What/Where are the 3 ways/peptidases that breakdown protein?

A

Luminal peptidases
Brush border peptidases
Cytosolic peptidases

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23
Q

What must proteins be digested into before they are taken up by enterocytes?

A

Oligopeptides and AA

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24
Q

Where are luminal peptidases secreted and where so they work?

A

Secreted by stomach and pancrease
(Pepsin; trypsin, chemo trypsin, carboxypeptidases)
Broken down into stomach and small intestine

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25
Q

What do brush border peptidases hydrolyze at apical membrane of enterocytes?

A

Oligopeptides —> AA and di/tripeptides

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26
Q

Where are cytosolic peptodases found?

A

Inside enterocytes
Di/tripeptidases —> AA to blood

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27
Q

What are the 5 Inactivated proenzymes/zymogens secreted by the pancreas ? Endo vs. Exo?

A

(ENDO)
Trypsin
Chymotrypsin
Elastase
(EXO)
Carboxypeptidase A
Carboxypeptidase B

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28
Q

What hydrolyses internal peptide bonds in proteins to make Oligopeptides (chains <6)?

A

Endopeptidases

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29
Q

What cleaves single AA from Carboxyl end of Oligopeptides?

A

Exopeptidases

30
Q

What exopeptidase prefers hydrophobic AA?

A

Carboxypeptidase A

31
Q

What exopeptidase targets basic AA like Lys and Arg?

A

Carboxypeptidase B

32
Q

Of the ENDOpeptidases which one produces basic Oligopeptides?

A

Trypsin (onto Carboxypeptidase B next!)

33
Q

What converts the inactive pancreatic zymogens to its active form?

A

Enterokinases

34
Q

What enzyme is essential for kick starting the breakdown of proteins by activating a cascade to activate other pro enzymes?

A

Trypsin activation cascade

Trypsinogen —> trypsin —> cascade)

35
Q

What actives protein digestion in the stomach under acidic conditions?

A

Pepsin

36
Q

What is activated in the small intestine and works at slightly more alkaline pH than teh stomach?

A

Pancreatic proteases (trypsinogen, chymotrypsinogen, procarboxypeptidase A & B)

37
Q

Where are amino acids cleaved from Oligopeptides with carboxypeptidases?

A

C-terminus

38
Q

What cleaves aromatic AA writhing peptide chains?

A

Chymotrypsin

39
Q

What happens to protein digestion if patients have a total gastrectomies or pernicious anemia?

A

Protein digestion and absorption remain intact
But will have B12 deficiency

40
Q

How are small Oligopeptides absorbed into enterocytes on the apical membrane?

A

H+/oligopeptide cotransporter (PepT1)

41
Q

How do AA from cytoplasmic hydrolysis exit the enterocyte (via BL membrane) ?

A

Na+ independent AA transporter

42
Q

How does AA enter the enterocyte from the apical side?

A

It needs a Na+ channel (dependent)

43
Q

What are the lipase sub and products?

A

Triglyceride —> (2) FA + monoglyceride

44
Q

What are the cholesterol ester hydrolase sub and products?

A

Cholesterol ester —> cholesterol + FA

45
Q

What are the phospholipids A2 sub and products?

A

Phospholipid —> Lysolecithin + FA

46
Q

What is the major form of dietary lipid?

A

TAG (triacylglycerols)

47
Q

What is the TAG structure?

A

(3) FA chains Esterified to a glycerol backbone

48
Q

What are other forms of dietary lipids aside form TAGs?

A

Phospholipids, cholesterol, free FA

49
Q

What initiates lipid digestion?

A

Lingual lipase (not significant)
@ mouth sent to stomach
+
Gastric lipase (partial digestion)
@ G cells gastrin

50
Q

What is gastric lipase resistant to in an acidic environment?

A

Pepsin

51
Q

What is a required to breakdown LCFA (long chain fatty acids) when lingual lipase and gastric lipase can’t finish the job?

A

Emulsification by bile salts
@ small intestine
+
Pancreatic lipase

52
Q

What are key hormones to regulate lipid digestion?

A

CCK and GIP

53
Q

What is release by duodenal mucosa in responses to FA to help regulate gastric emptying?

A

GIP (gastric inhib polypeptide)

54
Q

What is released in response to FA entering duodenum?

A

CCK (cholecystokinin)

55
Q

What does CCK do?

A

Stimulate bile salt release and pancreatic enzyme secretion

56
Q

What is the pancreatic lipase co-factor?

A

Colipase

57
Q

What is the major enzyme needed for TAG digestion in the small intestine?

A

Pancreatic lipase

58
Q

What is are the pancreatic lipase sub and hydrolyzed products?

A

TAG —> 2 MAGs + FFAs
(2 monoacylglycerols + free fatty acids)

59
Q

What do bile salts do?

A

Emulsify fat droplets to increase surface area and form micelles that transport digestion products to brush border for absorption

60
Q

How are bile salts recycled?

A

Enterohepatic circulation

61
Q

How are lipid digestion components taken up by enterocytes?

A

Direct diffusion or specific transporters

62
Q

What helps solubulize lipid digestion products allowing them to approach the intestinal epithelium?

A

Mixed Micelles

63
Q

What are micelles made up of?

A

Bile salts, fatty acids, 2 MAGs, cholesterol, and fat soluble vitamins

64
Q

What can diffuse directly across the intestinal epithelium and enter the portal circulation?

A

SCFA and MCFA (medium)

65
Q

LCFAs, 2-MAGs, lysophopholipids, and cholesterol need what in order to enter enterocytes?

A

FATP (FA transport proteins)

66
Q

What happens to LCFAs, 2-MAGs, and cholesterol once WITHIN enterocytes?

A

Re-esterification into TAG and Cholesterol esters
OR
Incorporated into chylomicrons

67
Q

What do chylomicrons do once they are created in the enterocytes?

A

Exocytosis into lymphatic vessels

68
Q

What does Vitamin B12 bind to in the stomach?

A

Haptocorrin

69
Q

What needs to happen to B12-haptocorrin in order for it to enter the Ilium (absorption) ?

A

Bind to IF

70
Q

What is B12 found in diet wise?

A

Animal products
Meat, fish, shellfish, eggs, milk

71
Q

Who’s at risk for a dietary cobalamin deficiency?

A

Strict vegetarians

GEM (28 decks)

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