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GIGU > Digestion and Absorption > Flashcards

Digestion and Absorption Flashcards

1
Q

What is lactose intolerance?

A

Lactase enzyme deficiency; lactose cannot be broken down so remains undigested and unabsorbed

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2
Q

Describe the sequence of events for lactose intolerance

A
  • Lactose remains in lumen and brings in H2O
  • Passes to the small intestine
  • Converted to SCFAs and hydrogen gas
  • Produces osmotic diarrhea
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3
Q

What are the carbohydrate digestion locations and which is the main one?

A

Mouth and Small intestine

- Small intestine = most breakdown done here

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4
Q

What enzyme in the mouth begins to break down starch?

A

Salivary amylase

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5
Q

What enzyme in the small intestine continues to break down starch?

A

Pancreatic amylase

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6
Q

What are some primary sugars?

A

Starch, lactose and sucrose

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7
Q

Where does most starch (carbohydrate) digestion and absorption occur?

A

Small intestines - duodenum

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8
Q

What is the site of activity for most digestive enzymes in the small intestine where large amounts of nutrients are absorbed?

A

Brush border - microvillar surface

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9
Q

Starch is broken down into?

A

Maltose - > Glucose + Glucose

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10
Q

Trehalose is broken down into?

A

Glucose + Glucose

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11
Q

Lactose is broken down into?

A

Glucose + Galactose

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12
Q

Sucrose is broken down into?

A

Glucose + Fructose

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13
Q

The brush border is important for what?

A

Digestion and absorption of many carbohydrates such as starch, lactose and sucrose

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14
Q

How does glucose or galactose get absorbed into the duodenal epithelial cell?

A

Secondary active transport using SGLT1

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15
Q

How does fructose get absorbed into the duodenal epithelial cell?

A

Facilitated diffusion using GLUT5

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16
Q

How does glucose, fructose, galactose reach the blood after being absorbed by duodenal epithelial cells?

A

Facilitated transport using GLUT2

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17
Q

What would need to be inhibited in order to inhibit glucose absorption?

A

SGLT1 transporter in the duodenal epithelial cells

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18
Q

What are 2 ways to test for carbohydrate assimilation disorders (malabsorption)?

A
  1. D-xylose test

2. Lactose/Sucrose/Methane breath tests

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19
Q

Describe the D-xylose test

A

Testing for abnormal carbohydrate assimilation;

  • Ingest D-xylose (pentose monosaccharide)
  • Measure urine excretion of D-xylose
    • Abnormal and LOW amounts of D-xylose in the urine = malabsorption of carbohydrates
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20
Q

What are the protein assimilation disorders?

A
  1. Chronic pancreatitis
  2. Congenital trypsin absence
  3. Cystinuria
  4. Hartnup’s disease
  5. Cystic Fibrosis
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21
Q

What are the main locations for protein digestion?

A

Stomach
Pancreas
Small intestine

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22
Q

What enzyme in the stomach can begin protein digestion?

A

Pepsin

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23
Q

What organs’ enzymes primarily break down proteins into di- and tripeptides and some amino acids?

A

Pancreatic enzymes

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24
Q

Where are most of the protein broken down pieces (di and tripeptides and amino acids) absorbed?

A

Small intestine

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25
Q

What 2 things can activate the pancreatic enzymes for protein digestion?

A

Enterokinase at the brush border in small intestine OR

Trypsin itself

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26
Q

Describe how to activate pancreatic enzymes for protein digestion

A

In the small intestine:

  • Trypsinogen is converted to Trypsin by ENTEROKINASE at brush border
  • Trypsin then activates ALL of the rest of the pancreatic enzymes
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27
Q

What are the main pancreatic enzymes that are activated by Trypsin?

A

Trypsin
Chymotrypsin
Elastase
Carboxypeptidase A and B

28
Q

Deficiency in pancreatic enzymes or defect in transporters of intestinal epithelial cells will result in?

A

Protein assimilation disorders

29
Q

Pancreatic enzymes are released as pro-enzymes, meaning what?

A

They are secreted into the duodenum (SI) as their inactive form; they will be activated by enterokinase at the brush border or by Trypsin itself

30
Q

Chronic pancreatitis

A

Deficiency in pancreatic enzymes = lack of proteases

- Cannot neutralize stomach acid as well

31
Q

Congenital Trypsin absence

A

Absence of Trypsin = ALL pancreatic enzymes are GONE and cannot be activated!

32
Q

Why is Congenital Trypsin absence so detrimental?

A

Trypsin activates ALL pancreatic enzymes for protein digestion - without trypsin they will not be activated for digestion

33
Q

Cystinuria

A

Defect in transport/uptake of basic AA

  • Kidney will be affected bc cannot absorb AA either
  • AA will be secreted in urine and feces
34
Q

Hartnup’s Disease

A

Defect in transport/uptake of neutral AA

  • Kidney will be affected bc cannot absorb AA either
  • AA will be secreted in urine and feces
35
Q

Cystic Fibrosis

A

CFTR Cl- channel mutation = impaired bicarbonate (HCO3-) secretion from the pancreatic ducts
- inability to neutralize stomach acid and incorrect functioning of proteases

36
Q

What are 2 lipid assimilation disorders?

A 
Celiac sprue (disease)
Tropical sprue
37
Q

What is celiac sprue?

A

Antibodies develop against gluten

- leads to destruction of intestinal villi and malabsorption of nutrients

38
Q

What are the symptoms of celiac sprue?

A

Abdominal pain, diarrhea, steatorrhea, weight loss, tingling in extremities

39
Q

Celiac sprue patients need to cut what out of their diet?

A

Gluten

40
Q

What is tropical sprue?

A

Infection causes loss of intestinal microvilli

- impaired lipid absorption

41
Q

Tropical sprue main symptom?

A

Diarrhea

42
Q

Where does most of lipid digestion occur?

A

Small intestine

43
Q

Enzyme found in the mouth for lipid digestion?

A

Lingual lipase

44
Q

CCK function for lipid digestion in the stomach?

A

Delays gastric emptying and increases gallbladder emptying

45
Q

What occurs in the small intestine for lipid digestion?

A

Bile salt emulsification with the help of pancreatic lipases

46
Q

What does pancreatic lipase need to displace bile salts in order to digest lipids?

A

Colipase

47
Q

Describe the order of events in the small intestine for lipid digestion

A
  • Bile salts form a micelle to solubilize TAGs
  • Micelle contents diffuse across SI cell membrane
  • Micelle contents are re-esterified
  • Formation of a chylomicron
  • Chylomicron is released in lymphatics
48
Q

Problems anywhere in the process of lipid digestion result in?

A

Steatorrhea

49
Q

Lipid digestion problems can arise if what 2 major players are dysfunctional?

A

Pancreatic enzyme secretions OR

Bile salt and micelle formation

50
Q

How does ileal resection affect lipid digestion?

A

Bile acids are recycle in the distal ileum for reuse. If there is no distal ileum, there will be deficient bile salts to create micelles for lipid digestion

51
Q

How does SIBO affect lipid digestion?

A

Small intestine bacteria overgrowth;

Bacteria deconjugates bile salts and will cause an impaired micelle formation if too much bacteria

52
Q

What are the fat soluble vitamins?

A

ADEK

53
Q

What are the water soluble vitamins?

A

B and C

54
Q

How are ADEK vitamins absorbed?

A

Same process as lipids

55
Q

How are B and C vitamins absorbed (besides B12)?

A

Na+ dependent transport

56
Q

What is vitamin B12 important for?

A

Metabolic functions
Nerve myelination
RBC maturation

57
Q

What is necessary for vitamin B12 absorption and where does it occur?

A

Intrinsic factor

Distal ileum

58
Q

Pernicious anemia

A

Failure of RBC to mature due to vitamin B12 deficiency due to failure of parietal cells in the stomach to release intrinsic factor

59
Q

What are 2 causes for pernicious anemia?

A
  1. Gastritis - inflammation of stomach kills parietal cells

2. Autoimmune - body attacks parietal cells or IF

60
Q

What 2 surgeries affect vitamin B12 absorption?

A

Gastrectomy

Gastric bypass

61
Q

Vitamin D is needed for?

A

Calcium absorption

62
Q

Vitamin C is needed for?

A

Iron absorption

63
Q

Jejunum absorbs what electrolyte?

A

Sodium

64
Q

Ileum absorbs and secretes which electrolytes?

A

Absorbs sodium

Secretes bicarbonate

65
Q

Colon absorbs and secretes which electrolytes?

A

Absorbs sodium

Secretes potassium

66
Q

Cholera toxin

A

Causes an increase in Cl- secretion in colon
- Na+ and H2O follow
= massive secretory diarrhea

GIGU (29 decks)

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