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Physiology section 3 > GI Lecture 51 > Flashcards

GI Lecture 51 Flashcards

1
Q

Absorption of carbohydrates, proteins, and lipids is highest where?

A

Duodenum

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2
Q

Absorption of calcium, folate, and iron is highest where?

A

Duodenum

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3
Q

Absorption of bile acids are highest where?

A

Terminal ileum

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4
Q

What carbohydrates are able to be absorbed?

A

monosaccharides

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5
Q

What is starch?

A

mixture of both straight and branch-chain polymers of glucose

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6
Q

Amylose

A

straight chain polymers

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7
Q

Amylopectin

A

branched-chain polymersq

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8
Q

Composition of Trehalose

A

2 glucose molecules

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9
Q

Composition of Sucrose

A

glucose and fructose

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10
Q

Composition of Lactose

A

glucose and galactose

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11
Q

What the three monosaccharides?

A
  • glucose
  • fructose
  • galactose
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12
Q

Name a carbohydrate that can’t be digested?

A

cellulose

-due to beta 1,4 linkages

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13
Q

Products of amylase digestion

A
  • alpha-limit dextrins
  • maltose
  • maltotriose
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14
Q

What digests alpha-dextrins?

A

-alpha dextrinase

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15
Q

What digests maltose?

A

-maltase

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16
Q

What digests maltotriose and sucrose?

A

-sucrase

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17
Q

What digests trehalose?

A

-trehalase

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18
Q

What digests lactose?

A

-lactase

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19
Q

SGLT1

A

simperer transports glucose or galactose against concentration gradient with sodium

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20
Q

What transporter allows glucose and galactose be reabsorbed?

A

GLUT2

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21
Q

Fructose transport (apical and basolateral)

A
  • GLUT5 (apical)

- GLUT2 special (basolateral)

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22
Q

Lactose Intolerance

A
  • Lack of lactase in the brush border

- lactose in lumen retains water and causes osmotic diarrhea

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23
Q

Congenital lactose intolerance

A
  • lack of jejunal lactase

- replace lactose with sucrose or fructose diet

24
Q

Glucose-galactose mal-absorption

A
  • mutation of SGLT 1
  • severe diarrhea
  • fructose diet
25
Q

Where and how is protein digestion started?

A

in the stomach with pepsin

26
Q

Two class of proteases for protein digestion

A
  • endopeptidases

- exopeptidases

27
Q

Five major pancreatic proteases secreted as inactive proteases

A
  • trypsinogen
  • chymotrypsinogen
  • proelastase
  • procarboxypeptidase A
  • procarboxypeptidase B
28
Q

What activates trypsin?

A

enterokinase (brush border enzyme)

29
Q

Into what must proteins be broken down into to be absorbed?

A
  • amino acids
  • dipeptides
  • tripeptides
30
Q

Explain absorption process of peptides and amino acids.

A
  • transport with Na+ and H+ symporter
  • dipeptides and tripeptides hydrolyzed into amino acids in epithelial cytosol
  • amino acids exit cell through facilitated diffusion
31
Q

Deficiency in single AA absorption

A

-compensated by absorption of di- and tri- peptides that are hydrolyzed in cells

32
Q

Trypsinogen deficiency

A
  • Diet of partially hydrolyzed proteins

- rare and serious

33
Q

Cystinuria

A
  • transporter for dibasic amino acids is absent in small intestine and kidney
  • result of intestinal defect is feces excretion, renal defect is urine excretion
34
Q

Major categories of lipid in the diet

A
  • Triglycerides
  • Phospholipids
  • Cholesterol
  • Vitamin A, D, E, K
35
Q

Emulsification

A
  • mixing of stomach churns dietary lipids into suspension of fine droplets
  • stomach emulsification by dietary proteins
  • small intestine emulsification by bile acids
36
Q

Lipolytic enzymes in pancreatic juice

A
  • Pancreatic lipase
  • Phospholipase A2
  • Cholesterol ester hydrolase
37
Q

Pancreatic lipase

A
  • hydrolyzes triglycerides to monoglycerides and fatty acids

- Bile acids inactivate pancreatic lipase, but collapse overrides this inactivation

38
Q

Phsopholipase A2

A
  • hydrolyzes phospholipids to lysolecithin and fatty acids

- secreted as proenzyme

39
Q

Cholesterol ester hydrolase

A
  • hydrolyzes cholesterol ester to free cholesterol and fatty acids
  • and ester linkages of triglycerides
40
Q

Composition of micelles

A
  • interior = lipid digestion products

- exterior = bile salts

41
Q

Lipid absorption inside cell

A
  • lipid digestion products are re-estrified
  • re-packaged with apoproteins into chylomicrons
  • exocytosed and enter lymphatic capillaries
  • empty into the thoracic duct an into bloodstream
42
Q

Pancreatic Insufficiency

A
  • results in defects of pancreatic enzyme secretion

- Abnormality of lipid digestion/absorption - results in steatorrhea

43
Q

Acidity of duodenal contents

A

-pancreatic enzymes cannot function optimally at acidic pH

44
Q

Deficiency of Bile salts

A
  • No micelle formation/interferes with lipid digestion/absorption
  • In ileal resection, bile lost in feces
45
Q

Abetalipoproteinemia

A
  • Failture to synthesize Apo B

- Chylomicrons are either not formed or unable to be transported into lymph

46
Q

How many liters of fluid absorbed in small intestine?

A

7 Liters

47
Q

How many liters of fluid absorbed in colon?

A

2 Liters

48
Q

How many liters of fluid excreted in feces?

A

100 - 200 mL

49
Q

There is a net absorption of ___ in ileum.

A

NaCl

50
Q

There is a net absorption of ___ in jejunum.

A

NaHCO3-

51
Q

Cholera

A
  • makes the adenylyl cyclase constitutively active and produces cAMP and keeps Chloride channel open
  • water follows and causes life-threatening diarrhea
52
Q

Calcium Absorption

A
  • Ca++ diffuses into cell from lumens side
  • Parathyroid hormone needs to convert dietary vitamin D into 1,25- dihydroxycholecalciferol
  • induces vitamin D- dependent Ca++ (calbindin D-28K)
  • pumped into blood by Ca++ ATPase
53
Q

Inadequate Ca++ absorption causes

A
  • rickets in children

- osteomalacia in adults

54
Q

Vitamin B12 Absoprtion

A
  • binds to R protein
  • pancreatic proteases degrade R proteins and B12 is transferred to Intrinsic Factor (IF)
  • Vitamin B12-IF complex absorbed in ileum
55
Q

Gastrectomy

A
  • parietal cells are lost
  • no B12 absorption
  • pernicious anemia (problem with RBC count)

Physiology section 3 (18 decks)

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