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Flashcards in Digestion and Absorption process of GI Deck (119):
1

Where does digestion start and end

begins in the stomach and ends in small intestine

2

Where does absorption take place

small intestine

3

2 main paths of absorption

cellular and paracellular

4

Cellular absorption

lumen --> apical membrane --> intestinal epithelial cell --> basolateral membrane --> bloof

5

Where are the transporters for cellular absorption

in membrane

6

Paracellular absorption

intestinal epithelial cell --> lateral intercellular space --> intestinal epithelial cell

7

2 types of digestive activity

cavital (luminal) digestion and membrane (contact) digestion

8

Cavital digestion

digestion from action of enzymes of salivary glands, stomach and pancreas

9

Membrane digestion

hydrolysis by enzymes of epithelial cells

10

Folds of Kerckring

longitudinal folds of small intestine

11

Function of villi and microvilli in small intestine

increase surface area

12

Where are the villi the longest and where are they the shortest

longest in duodenum and shorter in terminal ileum

13

Site of activity of digestive enzymes

microvillar surface

14

Barrier that allows some passage of nutrients, water, electrolytes

microvillar surface

15

Enterocytes

epithelial cells of intestine

16

Function of enterocytes

digestion, absorption, and secretion

17

Goblet cells

mucus-secreting cells

18

Function of goblet cells

physical, chemical and immunological protection

19

Paneth cells function

mucosal defense against infection and bacteria

20

What controls the flux of solutes and fluid between lumen and blood

enterocyte membrane

21

4 ways enterocytes move solutes and fluid

pinocytosis, passive diffusion, facilitated diffusion, and active trasport

22

Where does pinocytosis occur and whats its function

base of microvilli and used for uptake of protein

23

What movement takes place during absoprtion

transmural

24

Monosaccharides are absorbed by

enterocytes

25

Three end products of carbohydrate digestion

glucose, galactose, and fructose

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What does lactose break into

glucose and galactose

27

What does sucrose break into

glucose and fructose

28

What breaks down starch

alpha amylase

29

What can starch break into

maltose, dextrins, maltotriose

30

Transport mechanisms for absorption of carbs

co-transport and facilitated diffusion

31

GLUT 2

gets glucose, galactose and fructose from intracellular into blood

32

SGLT1

takes glucose and galactose out of the lumen into intracellular

33

GLUT5

takes fructose from lumen to intracellular

34

What kind of transport is SGLT 1

secondary active transport

35

Where is the Na/K ATPase located on the cells for carb absorption

basolateral side

36

Lactose intolerance

failure to digest carb

37

Why does lactose intolerance occur

brush-border lactase is lacking

38

Result of lactose intolerance

osmotic diarrhea-- undigested lactose remains in lumen and holds water

39

What happens to unabsorbed and undigested lactose

ferments into methane and hydrogen gas causing excess gas

40

How are proteins digested to absorbable forms

proteases in stomach and small intestine

41

Stomach protease

pepsinogen --> pepsin

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Small intestine proteases

trypsinogen --> trypsin, chymotrypsinogen --> chymotrypsin, proelastase --> elastase, proccarboxypeptidase (A or B) --> carboxypeptidase (A or B)

43

Endopeptidases

pepsin, trypsin, chymotrypsin, elastase

44

Exopeptidases

carboxypeptidase A and B

45

What does protein breakdown into in the stomach

amino acids and oligopeptides

46

What does protein breakdown into in the small intestine

amino acids --> dipeptides and tripeptides, oligopeptides --> amino acids --> dipeptides and tripeptides

47

Function of trypsin

catalyzes hydrolysis of trypsinogen (autocatalysis)

48

Transport mechanisms for absorption of proteins

co-transport and facilitated diffusion

49

Luminal cotransporters for amino acids

Na+/amino acid cotransporter -- one for each kind of amino acid - neutral, acidic, basic, and imino

50

How do dipeptides and tripeptides cross the luminal surface

H+/ Dipeptide or Tripeptide cotransporter

51

Basolateral (Blood) side of protein absorption

facilitated diffusion- one kind for each amino acid - neutral, acidic, basic, and imino

52

Disorders of protein assimilation

occur when there is a deficiency of pancreatic enzymes or transporter problem

53

Chronic pancreatitis and cystic fibrosis

deficiency of pancreatic enzymes

54

Congenital trypsin absence

absence of trypsin makes it seem like all pancreatic enzymes are gone

55

Cystinuria

genetic disorder where amino acids are secreted in the feces

56

Process of cystinuria

defect in or absence of Na+/amino acid co-transporter

57

Hartnup disease

can't absorb neutral amino acids (tryptophan)

58

Genetics of Hartnup disease

recessive genetic disorder

59

Symptoms of Hartnup disease

diarrhea, red scaly skin, photosensitivity, short stature

60

Urine samples of Hartnup disease

abnormally high excretion of neutral amino acids (trypotophan) and their by products (serotonin)

61

Cystic fibrosis transmembrane conductance regulator (CTFR)

chloride ion channel

62

Mutation in CTFR

associated with deficiency of pancreatic enzymes

63

What organ is the first to fail in cystic fibrosis

pancreas

64

How are lipids digested to absorbable forms

lipases in stomach and small intestine

65

Triglyceride breakdown into

via lingual, gastric, and pancreatic lipases into monoglyceride and 2 fatty acids

66

Cholesterol ester breakdown into

via cholesterol ester hydrolase into cholesterol and fatty acid

67

Phospholipid breakdown into

via phospholipase A2 into lysolechitin and fatty acid

68

Why lipid breakdown is complicated

lipids need to be solubilized in micelle and transported to apical membrane for absorption

69

Lingual and gastric lipases...

initiate lipid digestion in stomach

70

Where are lipid droplets emulsified

in stomach by dietary proteins -- with NO bile acids

71

What enzyme in the stomach helps lipid digestion and how

CCK because it slows gastric emptying allowing more time for breakdown

72

Where does most lipid digestion occur

small intestine

73

Function of bile salts

emulsify fat

74

Pancreatic enzyme and lipid digestion

enzymes secreted into small intestine to complete digesiton

75

Pancreatic lipase

inactivated by bile salts

76

Colipase

secreted an inactive for and activated by trypsin and binds to pancreatic lipase to displace the bile salt

77

Cholesterol ester hydrolase

catalyze cholesterol production and hydrolyze triglycerides into glycerol

78

Phospholipase A2

proenzyme is activated by trypsin

79

Optimal pH for pancreatic lipase

6

80

Products of lipid digestion

micelles

81

Micelle structure (5)

bile salt, hydrophilic side, hydrophilic side, nonpolar lipid and phospholipid

82

5 steps of processing a lipid

1.solubilization by micelles, 2.diffusion of micellar content across apical membrane, 3.reesterification, 4.chylomicron formation, 5.exocytosis of chylomicron
**includes Apo B ** on chylomicron

83

No ApoB on chylomicron can lead to

abetalippoproteinemia and you can't absorb dietary lipids

84

Abnormality of lipid assimilation

steatorrhea

85

Pancreatic insufficiency

failure to secrete adequate pancreatic enzymes

86

Function of pancreatic enzymes

regulate acidity of duodenum

87

Zollinger-Ellison syndrom

gastric secreting tumor causing H+ increase and overload of acid in duodenum

88

Pancreatitis

impaired HCO3 secretion and impaired enzyme secretion

89

Deficiency of bile salt

interferes with formation of micelles

90

Causes of bile salt deficiency

ileal resection and small intestinal bacterial overgrowth (SIBO)

91

Ileal resection and bile salt deficiency

interrupts enterohepatic circulation of bile salts and bile salt pool is reduced

92

Small intestinal bacterial overgrowth (SIBO)

bacteria deconjugate bile salts causing failure of micelle formation and fat malabsorption

93

Two main causes of small intestinal bacterial overgrowth

decrease in gastric acid secretion and small intestin dysmotility

94

Clinical presentation of SIBO

chronic diarrhea, weight loss, and malabsorption

95

Tropical sprue

reduction in number of intestinal epithelial cells which reduces microvillar surface area

96

Why is lipid absorption impaired in tropical sprue

because surface area for absorption is decreased

97

S/S of tropical sprue

steatorrhea, deficient in folate and B12, diarrhea

98

Treatment for tropical spure

tetracycline and folate

99

Non-tropical sprue (celiac sprue)

autoimmune disorder where antibodies develop against gluten

100

S/S of non-tropical sprue

malabsorption and deficiency in vitamin B12, folate, iron, calcium, vitamin D, and vitamin A

101

Prevalence of Non-tropical sprue

caucasian and european ancestry and woman

102

GI symptoms of celiac spure

abdominal pain, constipation, diarrhea, steatorrhea

103

Non Gi symptoms of celiac sprue (due to nutrient deficiency)

tingling in hands, itchy skin, easy bruising

104

Fat soluble vitamins

A, D, E, K

105

Mechanism of fat soluble absorption

same as lipids

106

Water soluble vitamins

B1,2,3,12, C, biotin, folic acid, nicotinic acid, and pantothenic acid

107

How are water soluble vitamins absorbed

Na+ dependent cotransport in small intestine

108

Vitamin B12 importance

complexes with other proteins-- R protins, intrinsic factor, and transcoalbumin II

109

2 disruptions in absorption of vitamin B12

gastrectomy and gastric bypass

110

Gastrectomy

loss of parietal cells and intrinsic factor source

111

Gastric bypass

exclusion of stomach, duodenum, and proximal jejunum alters absorption of vitamin B12

112

Pernicious anemia

stomach doesn't produce enough intrinsic factor and decrease in B12

113

Common causes of pernicious anemia

atrophic gastritis and autoimmune condition

114

Atrophic gastritis

chronic inflammation of stomach mucosa causing loss of parietal cells

115

Abnormalities of absorption of vitamin D

Rickets, osteomalacia due to inadequate Ca2+ absorption b/c deficient vitamin D

116

2 sources of D3 in vitamin D formation

Sunlight and Diet

117

Vitamin D effects of body (3)

increase in gut Ca2+ absorption, increase bone calcification and increase bone resorption

118

Enzyme that makes vitamin D usable to body

1 alpha hydroxylase

119

Usable form of vitamin D

1,25 Dihydroxy D3