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Physio II > Exam 4- Digestion and Absorption > Flashcards

Exam 4- Digestion and Absorption Flashcards

1
Q

Final breakdown of all food substances occurs where in the GI tract?

A

Small intestines

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2
Q

Absorption involves what type of movement of digested products to the general circulation?

A

Transmural

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3
Q

What is the 2 step breakdown of complex sugars?

A

Complex sugars –> (a-amylase) –> oligosacchariades –> simple sugars (monosaccharide)

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4
Q

What enzymes break down 1:4 alpha linkages only?

A

Salivary and pancreatic amylase

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5
Q

How are the majority of carbs ingested?

A

Complex polysaccharides

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6
Q

Pancreatic amylase can’t handle what starch linkage?

A

1:6 linkage

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7
Q

All oligosaccharides must be broken down into one of what 3 products to be absorbed?

A

Glucose, galactose, fructose

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8
Q

What type of proteins are synthesized by epithelial cells and are needed for the membrane digestion of oligosaccharides?

A

Intrinsic membrane proteins

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9
Q

What are the two main groups of the intrinsic membrane proteins?

A

Galactosidases and alpha glucosidases

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10
Q

Lactase is what type of intrinsic membrane protein?

A

Galactosidase

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11
Q

Sucrase, maltase, and alpha dextrinase are what type of intrinsic membrane proteins?

A

Alpha glucosidases

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12
Q

The majority (80%) of ingested carbs are digested to what?

A

Glucose

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13
Q

Glucose transport is primary or secondary active transport?

A

Secondary active (since plasma glucose concentration is high)

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14
Q

What transporter is Na-dependent entry at the apical membrane and facilitates the movement of glucose and galactose into the cell?

A

SGLT-1 transporters

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15
Q

What transporter on the basolateral membrane is involved with transport of glucose and galactose to the interstitium via facilitated diffusion?

A

GLUT2

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16
Q

What transports fructose (w/o energy) on the apical membrane into the cell?

A

GLUT 5

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17
Q

Most disorders of carbohydrate digestion and absorption are due to what?

A

Deficiencies that prevent breakdown of carbs to an absorbable form

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18
Q

What breaks down lactose? What are the end products?

A

Lactose → glucose and galactose, via lactase

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19
Q

What breaks down sucrose? What are the end products?

A

Sucrose → glucose and fructose, via sucrase

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20
Q

What breaks down a-dextrins? What is the end product?

A

Alpha-dextrins → glucose, via maltase and alpha-dextrinase

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21
Q

What breaks down maltotroise? What is the end product?

A

Maltotriose → glucose, via maltase, sucrase, alpha-dextrinase

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22
Q

What breaks down maltose? What is the end product?

A

Maltose → glucose, via maltase, sucrase, alpha-dextrinase

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23
Q

Unabsorbed carbs hold water osmotically and cause what clinical condition?

A

Osmotic diarrhea (lumen is isosmotic to interstitium)

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24
Q

What are the 3 clincal sx of unabsorbed lactose?

A

Osmotic diarrhea, cramps, abd distension

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25
Q

What is a potential consequence of long-term intestinal disease?

A

Lactase deficiency (membrane lactase dysconfigured)

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26
Q

What is the primary enzyme in luminal digestion?

A

Amylase

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27
Q

What are the products of protein digestion? (2)

A

Amino acids and oligopeptides

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28
Q

Where are the proenzymes of protein digestion stored?

A

Pancreas

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29
Q

What happens if the proenzymes of protein digestion become active before being released from the pancreas?

A

Pancreatitis

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30
Q

What enzyme is required to activate the proenzymes of protein digestion?

A

H+ to activate pepsinogen to pepsin

Enterokinase to activate trypsinogen to trypsin

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31
Q

Proteins make up 20-35% of caloric intake with a significant amount coming from where?

A

Endogenous sources (desquamated cells and gastric secretions)

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32
Q

The final breakdown of proteins occurs where?

A

Brush border via peptidases

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33
Q

Amino acids are co-transported into the cell with what?

A

Sodium gradient via 2˚ active transport

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34
Q

How are di and tripeptides co-transported in the cell?

A

Coupled w/ H+ transport via 2˚ active trasport

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35
Q

In addition to peptidase breakdown in the brush border layer, how else are proteins digested? (2)

A

Amino acid carriers and endocytosis (neonates)

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36
Q

Decreased protein absorption as a result of pancreatic insuffiency will lead to what?

A

Malnutrition

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37
Q

Pancreatic insufficiency will have what effect on the amount of trypsin that reaches the intestines?

A

Decreased/insufficienct amounts of trypsin

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38
Q

What condition is a congential defect in transport of neutral amino acids?

A

Hartnup disease (absorption of di- and tripeptides ok)

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39
Q

In what condition is the transporter for dibasic amino acids absent from the gut and kidney resulting in the loss of dibasic amino acids in urine and feces?

A

Cystinuria

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40
Q

What motion is required for the digestion of fats due to their insolubility and tendency to coalesce?

A

Churning and bile emulsification

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41
Q

What are the 4 key events in fat digestion?

A

Secretion of bile and lipases, emulsification of fats by bile, enzymatic hydrolysis of ester linkages, solubilizing digestion products within micelles for delivery to enterocytes

42
Q

What enzyme is primary responsible for the digestion of fats?

A

Pancreatic lipase (lingual lipase plays small role)

43
Q

Pancreatic lipase requires assistance from what other enzyme?

A

Colipase (prevents bile salt inhibition of this enzyme)

44
Q

What eznymes removes fatty acid moiety from cholesterol, vitamins A, D, E, and glycerides and can remove all three ester linkages?

A

Cholesterol ester hydrolase

45
Q

What enzyme hydrolyzes phospholipids at 2 position in fat digestion?

A

Phospholipase A2

46
Q

Products of fat digestion are removed quickly by the formation of what?

A

Micelles

47
Q

Once triglycerides are broken down, they combine with bile acids to form micelles. How is the micelle absorbed?

A

Diffuse across the unstirred layer to the mucosal surface of the apical membrane of the enterocyte where it breaka down and its contents absorbed by simple diffusion

48
Q

What are the components of a micelle? (breaken down into these components for simple diffusion) (4)

A

Long-chain FFA, 2-MG, phospholipids, cholesterol

49
Q

How much of ingested fat is removed by the small intestine?

A

95%

50
Q

What happens to the components of micelles once they pass into the enterocyte via simple diffusion?

A

Reassemble TG and phospholipids

51
Q

What structure has a TG and cholesterol core is surrounded by phospholipids and apoproteins?

A

Chylomicron

52
Q

How does a chylomiron re-enter blood circulation? (3 steps)

A

Exocytosed and enters lacteal → lacteal transports chylomicron into general lymph → into blood stream

53
Q

Chylomicrons carry triglycerides to what tissues? (3)

A

Adipose tissue, skeletal muscle, cardiac muscle

54
Q

What makes up the majority of a chylomicron?

A

Triglycerides (> cholesterol, PLs, apoproteins)

55
Q

Zollinger Ellison syndrome results in abnormal lipid digestion or lipid absorption?

A

Lipid digestion

56
Q

What syndrome causes dysfunctional lipolysis as a result of a gastrin secreting tumor in duodenum or pancreas that creates an acidic small intestine and dysfunctional pancreatic lipase?

A

Zollinger Ellison syndrome

57
Q

What rare disease causes steatorrhea due to abnormal lipid absorption caused by generalized lymphatic dystrophy?

A

Whipple’s disease

58
Q

Whipple’s disease results in abnormal lipid digestion or lipid absorption?

A

Lipid absorption

59
Q

What enzymes are produced in the pancreas? (8)

A

Amylase, trypsin, chymotrypsin, carboxypeptidase, elastase, lipase-colipase, phospholipase A, cholesterol esterase nonspecific lipase

60
Q

What enzymes are produced in the brush border? (8)

A

Enterokinase, disaccharidases, maltase, sucrase, lactase, peptidases, aminooligopeptidase, dipeptidase

61
Q

What dictates the vitamin absorption mechanism?

A

Solubility

62
Q

What are the fat soluble vitamins? (4)

A

A, D, E, K

63
Q

What are the water soluble vitamins? (8)

A

B1, B2, B6, B12, C, biotin, folate, pantothenic acid

64
Q

How are fat soluble vitamins solubilized/ transported and how do they enter circulation?

A

Micelles, chylomicrons

65
Q

How are most water soluble vitamins absorbed?

A

Via Na+ dependent co-transport (exception is B12)

66
Q

How is vitamin B12 absorbed?

A

Binds to gastric intrinsic factors which protects it from digestion, then absorbed in ileum

67
Q

What is the main MOA for calcium reuptake in the intestines?

A

Upregulation of calcium binding protein (CaBP = rate limiting) present in enterocytes

68
Q

Ca passivley enters the enterocyte and is transported via what to the basolateral membrane?

A

CaBP (binding protein)

69
Q

What are the 2 mechanisms for movement of calcium on the basolateral membrane of the intestines?

A

Ca-ATPase (active) and NaCa exchanger (passive)

70
Q

Does PTH have a direct effect on Ca absorption in the enterocyte?

A

No

71
Q

What is calcium absorption regulated by?

A

PTH and vitamin D

72
Q

How much iron is ingested vs absorbed?

A

Amount ingested >> amount absorbed

73
Q

What promotes intestinal absorption and solubilization of iron?

A

Gastric acid (reduces Fe3+ to Fe2+)

74
Q

What binding protein is required for plasma transport of iron?

A

Transferrin

75
Q

What is the preferred form of iron within the body?

A

Ferrous (Fe2+)

76
Q

What is the intracellular storage depot for iron that allows for the release of iron in a controlled fashion?

A

Ferritin (iron binding protein)

77
Q

When is ferritin lost?

A

When enterocyte is sloughed off

78
Q

What is the single biggest source of ingested and secreted fluids?

A

Pancreatic juice and bile (diet contributes ~2/10 L)

79
Q

What is the primary site of water and electrolyte absorption?

A

Small intestine (then colon)

80
Q

What organ is impermeable to water?

A

Stomach

81
Q

What is the driving force for water movement?

A

Solute transport (Na)

82
Q

What is the 1st site for Na+ absorption?

A

Small intestine (mechanism similar to proximal tubule, Na/H exchagner maintained by Na-K-ATPase)

83
Q

What part of the intestines has a net reabsorbtion of Na and HCO3 (+sugar, and AA)?

A

Jejunum

84
Q

What are the effects of Na+/H+ exchange in the jejunum? (2)

A

Acidifies lumen and neutralizes lumenal HCO3-

85
Q

What drives paracellular Cl- absorption?

A

Voltage gradient

86
Q

What portion of the intestines does the following occur:

Both H+ and HCO3 are secreted into the lumen (resulting in NO pH change) to drive transport of Na and Ca in the cell

A

Ileum

87
Q

What is the net reabsorption activity of the ileum?

A

Recovery of sodium and chloride (+ sugar and amino acids)

88
Q

What transporters contribute to chloride being reabsorbed into cells in the ileum? (2)

A

Apical chloride-HCO3 antiporter and Na/H exchanger

89
Q

Passive Na and K channels in the apical membrane of the colon responsible for what?

A

Na absorption (into the cell) and K secretion (into the lumen of the colon)

90
Q

ENaC is induced by what in the colon?

A

Aldosterone

91
Q

What is K secretion dependent on in the colon?

A

“Flow dependent”

92
Q

What is the effect of diarrhea on the colon?

A

Increase K+ loss due to increased flow of chyme through the colon

93
Q

Diarrhea is often associated with loss of what 3 things?

A

Fluid, HCO3- (causes metabolic acidosis), loss of K+ (hypokalemia)

94
Q

Diarrhea will result in electrolyte imbalances that manifest as what?

A

Metabolic acidosis and hypokalemia

95
Q

What is the result of decreased/ impaired surface area of the small intestine? (ex Crohns)

A

Diarrhea

96
Q

What is the result of osmotic diuresis due to unreabsorbable osmolytes? (ex. lactase enzyme deficiency)

A

Diarrhea

97
Q

What is a common cause of secretory diarrhea?

A

Cholera

98
Q

What can occur if chloride secretion in the colon is increased?

A

Secretory diarrhea

99
Q

What is the MOA for cholera? (4 steps)

A
  1. Cholera toxin binds to apical membrane of crypt cells
  2. Irreversible activation of adenylate cyclase
  3. Increased cAMP production/ activity which opens Cl- channels
  4. Increased secretion of Cl- on the apical membrane
100
Q

What is the treatment for secretory diarrhea?

A

Oral rehydration therapy (and control presence of vibrio cholerae)

101
Q

What maintains the Na and Cl concentration gradients within the epithelials cells of the colon?

A

NaKCC1 transporter (Na, K, 2 Cl) maintained by Na/K-ATPase

Physio II (14 decks)

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