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

Ch. 11: GI Digestion & Absorption Flashcards

1
Q

What regulates secretory & absorptive activities of GI tract?

A

Hormones

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2
Q

Layers of GI tract (IN ➡️ OUT)?

A

Mucosa
Submucosa
Muscularis
Serosa

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3
Q

Saliva: pH?

principle ions?

A

pH 7.0 (hypotonic)

Na+, K+, Cl-, HCO3-

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4
Q

Catalytic fxn of amylase?

A

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

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5
Q

What cell form & secrete bile? Shape of cells?

A

Hepatocytes

Polygon

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6
Q

What does bile contain?

A 
Bile acids
Bile pigments
Cholesterol
Phosphatidylcholine
Electrolytes
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7
Q

⬆️ conjugated bilirubin = problem with?

A

Gallbladder ➡️ duodenum pathway

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8
Q

⬆️ unconjugated bilirubin = problem with?

A

Liver

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9
Q

Endocrine hormones of pancreas?

A

Insulin
Glucagon
Somatostatin

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10
Q

Exocrine fxn of pancreas?

A

Synthesize & secrete digestive enzymes & HCO3- rich fluid

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11
Q

Proenzymes in pancreatic juice?

A

Trypsinogen
Chymotrypsinogen
Procarboxypeptidase
Proelastase

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12
Q

What converts trypsinogen ➡️ trypsin?

Where?

A

Enteropeptidase

Brush border of jejunal mucosa

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13
Q

Fxn of trypsin inhibitor in pancreatic juice?

A

Protects against indiscriminate autodigestion from intraductal activation of trypsinogen

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14
Q

Major fxn of large intestine?

A

Absorb water, Na+ & other electrolytes

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15
Q

What type of bacteria is in large intestine?

Fxn?

A

Anaerobic

Metabolize CHO ➡️ lactate, short chain FAs, & gases

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16
Q

Gastrin: Sources?

A

G cells (gastric antrum, duodenum)

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17
Q

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

Ex?

A

Hypoglycemia

⬆️ Ca2+

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18
Q

What suppresses gastrin?

A

Acidification of antral mucosa

All members of secretin family

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19
Q

Gastrin: fxn?

A 
HCl secretion (parietal cells)
Pepsin secretion (chief cells)
Histamine secretion (enterochromaffin-like cells)
⬆️ gastric mucosal blood flow
Gastric motility
Proliferation of gastric mucosa
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20
Q

What is Zollinger-Ellison syndrome?

A

Tumors in stomach (keep secreting acid)

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21
Q

Ghrelin: Sources?

Fxn?

A

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

Promote food intake
Promote gastric motility
Stimulate growth hormone secretion

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22
Q

Cholecystokinin: Sources?

Fxn?

A

I cells of duodenum & jejunum, CNS

stimulate gall bladder & pancreatic secretions
Decrease appetite

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23
Q

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

Fxn?

A

K cells (duodenum & jejunum)

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

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24
Q

Secretin: Sources?

Fxn?

A

S cells (upper portions of small intestine)

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

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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

Medical Biochemistry (23 decks)

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