Ch. 11: GI Digestion & Absorption Flashcards Preview

Medical Biochemistry > Ch. 11: GI Digestion & Absorption > Flashcards

Flashcards in Ch. 11: GI Digestion & Absorption Deck (61):
1

What regulates secretory & absorptive activities of GI tract?

Hormones

2

Layers of GI tract (IN ➡️ OUT)?

Mucosa
Submucosa
Muscularis
Serosa

3

Saliva: pH?

principle ions?

pH 7.0 (hypotonic)

Na+, K+, Cl-, HCO3-

4

Catalytic fxn of amylase?

Hydrolysis of alpha (1➡️4) glycosidic linkages of starch & glycogen

5

What cell form & secrete bile? Shape of cells?

Hepatocytes

Polygon

6

What does bile contain?

Bile acids
Bile pigments
Cholesterol
Phosphatidylcholine
Electrolytes

7

⬆️ conjugated bilirubin = problem with?

Gallbladder ➡️ duodenum pathway

8

⬆️ unconjugated bilirubin = problem with?

Liver

9

Endocrine hormones of pancreas?

Insulin
Glucagon
Somatostatin

10

Exocrine fxn of pancreas?

Synthesize & secrete digestive enzymes & HCO3- rich fluid

11

Proenzymes in pancreatic juice?

Trypsinogen
Chymotrypsinogen
Procarboxypeptidase
Proelastase

12

What converts trypsinogen ➡️ trypsin?

Where?

Enteropeptidase

Brush border of jejunal mucosa

13

Fxn of trypsin inhibitor in pancreatic juice?

Protects against indiscriminate autodigestion from intraductal activation of trypsinogen

14

Major fxn of large intestine?

Absorb water, Na+ & other electrolytes

15

What type of bacteria is in large intestine?

Fxn?

Anaerobic

Metabolize CHO ➡️ lactate, short chain FAs, & gases

16

Gastrin: Sources?

G cells (gastric antrum, duodenum)

17

Gastrin: Released due to chem, mech, neuronal stimulation of G cells

Ex?

Hypoglycemia

⬆️ Ca2+

18

What suppresses gastrin?

Acidification of antral mucosa

All members of secretin family

19

Gastrin: fxn?

HCl secretion (parietal cells)
Pepsin secretion (chief cells)
Histamine secretion (enterochromaffin-like cells)
⬆️ gastric mucosal blood flow
Gastric motility
Proliferation of gastric mucosa

20

What is Zollinger-Ellison syndrome?

Tumors in stomach (keep secreting acid)

21

Ghrelin: Sources?

Fxn?

A cells of gastric fundus, other GI tract segments, hypothalamus

Promote food intake
Promote gastric motility
Stimulate growth hormone secretion

22

Cholecystokinin: Sources?

Fxn?

I cells of duodenum & jejunum, CNS

stimulate gall bladder & pancreatic secretions
Decrease appetite

23

Gastric Inhibitory Peptide (GIP) / Glucose-dependent insulinotropic polypeptide: Sources?

Fxn?

K cells (duodenum & jejunum)

Insulin secretion (beta-cells of pancreas)
Inhibits gastric secretion & motility
Stimulate FA synthesis in adipose tissue

24

Secretin: Sources?

Fxn?

S cells (upper portions of small intestine)

Secretion of bicarb-rich fluid (duct cells & biliary tract)
Augments action of CCK
⬇️ gastric acid secretion

25

Polypeptide YY: Sources?

Fxn?

L-cells (distal small & large intestines)

Inhibits food intake

26

Somatostatin: Sources?

Fxn?

D-cells (pancreas & GI tract), hypothalamus

Inhibits secretion of GI tract hormones, growth hormone, & thyrotropin

27

Glucagon-like peptide-1 (GLP-1): Sources?

Fxn?

L-cells (small & large intestines)

Promotes insulin secretion from beta-cells (pancreas)
Promotes beta-cell growth
Suppresses glucagon secretion from alpha-cells (pancreas)
Delays gastric emptying

28

Glucagon-like peptide-2 (GLP-2): Sources?

Fxn?

L-cells (distal small & large intestines)

Promotes intestinal mucosal growth & repair
Inhibits gastric secretion

29

Oxyntomodulin: Sources?

Fxn?

L-cells (distal small & large intestines)

Inhibits food intake
Inhibits gastric motility & acid production

30

Endopeptidases: Digest ? ➡️ Into ?

Interior peptide bonds ➡️ peptides

31

Exopeptidase: Digest ? ➡️ Into ?

Terminal peptide bonds ➡️ a.a.

32

What things stimulates acid secretion?

Ach
Gastrin
Histamine (H2 receptor)
Bombesin

33

What things suppress acid secretion?

Anticholinergic agents (atropine)
H2 receptor antagonists (cimetidine, ranitidine)
Prostaglandin E derivatives
Substituted benzimidazoles (omeprazole, pantoprazole)

34

Digestion & absorption: CHO

Step 1?

Intraluminal hydrolysis via alpha-amylase:

starch & glycogen ➡️ oligosaccharides

35

Digestion & absorption: CHO

Step 2?

Brush-border surface hydrolysis via oligosaccharidases:

Oligosaccharides & disaccharides ➡️ monomers

36

Digestion & absorption: CHO

Step 3?

Transport of monosaccharides ➡️ enterocytes (Na/K-ATPase, semi-active transport)

37

3 examples of CHO intolerance?

Lactose
Sucrose
Alpha-limit dextrin

38

3 types of endogenous proteins? Grams per day digested?

1) secreted from GI tract organs & glands (20-30 g/d)
2) turnover of GI epithelium (30 g/d)
3) plasma proteins diffusing ➡️ intestinal tract (1-2 g/d)

39

Major products of intraluminal digestion of protein?

a.a. (30-40%)
small peptides (60-70%)

40

4 active, carrier-mediated, Na+ dependent transport systems for free a.a.? Disorders associated with defects in each?

1) neutral a.a. ➡️ Hartnup disease
2) basic a.a. & cystine ➡️ cystinuria
3) asp & glu ➡️ dicarboxylic aminoaciduria
4) gly & imino acids ➡️ aminoglycinuria

41

How are dipeptides & tripeptides transported into enterocytes?

Actively transported by Na-dependent mechanism

42

Neonates have ability to absorb intact proteins after birth ➡️ allows them to do what?

Acquire passive immunity (absorbs Igs in colostrum)

43

3 phases of lipid digestion?

1) luminal
2) intracellular
3) secretary

44

4 diff phospholipases?

A1, A2, C, D

45

What is celiac disease (gluten-sensitive enteropathy)?

Gliadins ➡️ production of Ab to endomysium of smooth muscle

46

What is cystic fibrosis?

Multiple exocrinopathy & malabsorption due to lack of pancreatic enzymes ➡️ SI

47

What is chronic alcoholism?

Malabsorption of foods & vitamins (due to liver and pancreas involvement, mucosal dysfunction)

48

Lipid digestion abnormalities: rapid gastric emptying

Biochem disturbance & ex of disease?

⬇️ efficiency of lipid interaction w/bile & pancreatic secretions

Gastrectomy (Tx ulcers or neoplasms in stomach)

49

Lipid digestion abnormalities: acidic duodenal pH

Biochem disturbance & ex of disease?

Inactivate pancreatic lipase
⬇️ ionization of bile acids

Zollinger-Ellison syndrome

50

Lipid digestion abnormalities: ⬇️ CCK

Biochem disturbance & ex of disease?

Deficiency of bile & pancreatic secretions

Mucosal destruction disorders
regional enteritis
gluten enteropathy

51

Lipid digestion abnormalities: congenital lipase/colipase deficiency

Biochem disturbance?

Defective lipolysis

52

Lipid digestion abnormalities: pancreatic insufficiency

Biochem disturbance & ex of disease?

Defective lipolysis

Chronic pancreatitis
pancreatic duct obstruction (CF)

53

Lipid digestion abnormalities: absent/⬇️ bile salts

Biochem disturbance & ex diseases?

⬇️ lipolysis (due to impaired micelle formation)

See table 11.3

54

Define diarrhea? (Volume)

Amt of water excreted in feces > 500 mL

55

Describe process of water absorption

Passive process

Coupled to transport of organic solutes & electrolytes (glucose & a.a.)

56

What regulates absorption of Na+?

Aldosterone

57

How is K+ absorbed?

Passive diffusion

58

Impact of cholera & pertussis toxins on cell regulation pathways? (disorders of fluid/electrolyte absorption)

Cholera: ADP-ribosylation of Gs-alpha

Pertussis: ADP-ribosylation of Gi-alpha

59

Impact of diphtheria toxin on cell regulation pathways? (disorders of fluid/electrolyte absorption)

ADP-ribosylation of EF2 ➡️ inhibits euk pro synthesis

60

Disorders of fluid/electrolyte absorption: impact of E. coli?

Non-bloody diarrhea
Hemorrhagic colitis
Hemolytic uremic syndrome
Death

61

Disorders of fluid/electrolyte absorption: pancreatic islet-cell tumor

Impact?

severe watery diarrhea