Digestion/Absorption

Question 1

Folds of Kercking

Answer 1

Longitudinal folds on luminal surface of small intestine

Question 2

Brush border

Answer 2

Increases surface area and is site of activity for numerous digestive enzymes

Question 3

Enterocytes

Answer 3

• Epithelial cells

- Focusing on digestion, absorption, secretion

Question 4

Goblet cells

Answer 4

Mucus-secreting cells for protection

Question 5

Paneth cells

Answer 5

Part of mucosal defenses against infection that secrete agents to destroy bacteria or produce inflammation

Question 6

Effect of terminal ileal resection?

Answer 6

• Abolished bile salt and Vitamin B12 absorption

Question 7

Carb Digestion (mouth)

Answer 7

• Some starch broken down
• Salivary amylase
• Starch broken into maltose and polymers of glucose

Question 8

Carb digestion (SI)

Answer 8

• Most starch breakdown occurs here
• Pancreatic amylase *
• Starch – maltose and polymers of glucose

Question 9

Maltose becomes

Answer 9

Glucose + Glucose

Question 10

Trehalose becomes

Answer 10

Glucose + Glucose

Question 11

Lactose becomes

Answer 11

Galactose + Glucose

Question 12

Sucrose becomes

Answer 12

Glucose + Fructose

Question 13

Monosaccharide transporters from lumen to duodenal epithelial cell?

Answer 13

SGLT1 + GLUT5

Question 14

SGLT 1

Answer 14

secondary active transporter for glucose and galactose (from lumen to epithelial cell)

Question 15

GLUT 5

Answer 15

facilitated diffusion for fructose (from lumen to epithelial cell)

Question 16

GLUT 2

Answer 16

facilitated diffusion into blood (from epithelial cell to blood)

Question 17

Transporters from epithelial cell to blood

Answer 17

• Na/K ATPase

- GLUT 2

Question 18

What results from lactose intolerance?

Answer 18

Lactose stays in lumen, holds H2O in lumen and osmotic diarrhea results

Question 19

D-xylose test

Answer 19

• Pt ingests 25 g D-xylose and urine collected for 5 hrs
• 4g+ in urine = absorbed properly
• < 4 g in urine = not properly absorbed (some absorption disorder present)

Question 20

Endopeptidases

Answer 20

hydrolyze interior bonds

pepsin, trypsin, chymotrypsin, elastase

Question 21

Exopeptidases

Answer 21

hydrolyze one amino acid at a time from carboxyl end

carboxypeptidase A/B

Question 22

Protein digestion (stomach)

Answer 22

• 10-20% breakdown occurs here (not essential)

- Pepsin (pepsinogen activated at pH 2,3)

Question 23

Protein digestion (pancreas)

Answer 23

• Proteins broken down into di/tri peptides

- Trypsin, chymotrypsin, carboxypeptidase, elastase

Question 24

Role of trypsin and chymotrypsin in protein digestion

Answer 24

Cleaves into small polypeptides

Question 25

Role of carboxypeptidase in protein digestion

Answer 25

Cleaves AA into carboxyl ends

Question 26

Protein digestion (SI)

Answer 26

- Aminopolypeptidase, dipeptidases | - AA/peptides absorbed into enterocytes

Question 27

What enzyme(s) activate zymogens?

Answer 27

Trypsin or enterokinase (trypsinogen)

Question 28

Co-transport of AAs in SI

Answer 28

Travel with Na+ in co-transporters | Peptides travel w/ H+

Question 29

Chronic pancreatitis

Answer 29

Deficiency of pancreatic enzymes (ie. lack of proteases)

Question 30

Congenital trypsin absence

Answer 30

No trypsin... no functional pancreatic enzymes

Question 31

Cystinuria

Answer 31

- Defect in/absence of Na+/AA cotransporters | - Dibasic AA (Cys, Lys, Arg, Orn) transporters specifically

Question 32

Hartnup disease

Answer 32

- SI cannot absorb neutral AAs | - Sx resemble pellagra (dementia, diarrhea, dermatitis)

Question 33

Cystic Fibrosis

Answer 33

- CFTR-regulated Cl- channel on apical membrane w/ mutation - Mutation causes loss of HCO3- secretion (enzymes cannot move from ducts -- pancreatitis) - Autodigestion of pancreas possible

Question 34

Biggest issue with lipid digestion

Answer 34

Insolubility of lipids

Question 35

Lipid digestion (stomach)

Answer 35

- Lingual/gastric lipase act on TAGs (10% TAG absorption) | - Time required for CCK to act... so CCK inhibits gastric emptying to allow time for more mixing and GB emptying

Question 36

Lipid digestion (SI)

Answer 36

- Majority of digestion here - Bile salts emulsify fats - Variety of enzymes secreted into SI to facilitate digestion

Question 37

Pancreatic lipase

Answer 37

- Secreted as active | - Inactivated by bile salts w/o colipase (which is activated by trypsin to displace bile salts)

Question 38

Cholesterol ester hydrolase

Answer 38

- Secreted as active - catalyzes production of free cholesterol - TAG -- glycerol

Question 39

Phospholipase A2

Answer 39

- Secreted as proenzyme | - Breaks down phospholipids

Question 40

Steps in fat absorption

Answer 40

1. Solubilization by micelles (apical side) 2. Diffusion of micellar content across apical membrane 3. Reesterification 4. Chylomicron formation 5. Exocytosis of chylomicrons into lymphatics (through BL)

Question 41

Component needed for lipid absorption

Answer 41

ApoB (w/o it you get abetalipoproteinemia)

Question 42

Key indication of lipid absorption issue

Answer 42

Steatorrhea

Question 43

Key theme of lipid absorption issue

Answer 43

Improper acidity of duodenal contents (too much acid/not enough HCO3-)

Question 44

Factors causing bile salt deficits

Answer 44

- Ileal resection | - Small intestinal bacterial overgrowth (bacteria deconjugate bile salts, which impairs micelle formation)

Question 45

Problems with tropical sprue

Answer 45

- Loss/decreased number of intestinal epithelial cells - Reduced microvilli surface area - Fat soluble vitamins also afected - Diarrhea main indication

Question 46

Small intestine bacterial overgrowth

Answer 46

- Inappropriate growth of bacteria - Malabsorption - Breath test can indicate methane or hydrogen

Question 47

Common causes of pernicious anemia

Answer 47

1. Atrophic gastritis (chronic inflammation -- loss of parietal cells) 2. Autoimmune metaplastic atrophic gastritis (immune systems attacks IF)

Question 48

Significance of gastric bypass/gastrotomy

Answer 48

- Loss of parietal cells -- loss of IF -- Pernicious anemia

Question 49

Iron Absorption

Answer 49

- Liver secretes apotransferrin into bile - Apotransferrin binds with Fe/Hb to form transferrin - Vitamin C aids in process - Fe3+ to Fe2+

Question 50

Main site of absorption for most nutrients/vitamins

Answer 50

Small intestine