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GEMS > GI Nutrient Digestion & Absorption > Flashcards

GI Nutrient Digestion & Absorption Flashcards

1
Q

Where is the greatest amount of absorption? What is absorbed?

A

Duodenum
CHOs, proteins, lipids

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2
Q

Where are fatty acids absorbed?

A

Colon

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3
Q

What is absorbed in the small intestine?

A

Carbs, proteins, lipids (greatest in duodenum)

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4
Q

Where are Ca++, Fe+++, folate absorbed?

A

Actively absorbed in the duodenum

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5
Q

Where is bile acid absorbed?

A

Along the entire small intestine.

Only active absorption in ileum

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6
Q

Where is B12 (cobalamin) absorbed

A

Ileum (ONLY)

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7
Q

What process is defective in Celiac Disease?

A

Fat absorption & Lactose hydrolysis

In the duodenum and jejunum

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8
Q

What process is defective in Chronic pacreatitis?

A

Fat digestion

In the exocrine pancreas

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9
Q

What process is defective in Crohn disease (or surgical resection) of ileum?

A

Cobalamin & bile acid absorption

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10
Q

What process is defective in primary lactase deficiency?

A

Lactose hydrolysis in the small intestine

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11
Q

What occurs as a result of intraluminal hydrolysis?

A

Starch breaks down into oligosaccharides by hydrolysis via salivary a-amylases & pancreatic a-amylases

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12
Q

Amylases are produced in what cells?

A

Acinar cells of salivary glands & pancreas

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13
Q

Carb Metabolism: What are the products of intraluminal hydrolysis (step 1)?

A
  1. Linear glucose oligomers
  2. Maltotriose (linear glucose trimer)
  3. Maltose (linear glucose dimer)
  4. a-limit dextrins (contain a-1,6 branching)
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14
Q

Carb Metabolism: Membrane Digestion (step 2) – function

A

Digest oligosaccharides into monosaccharides

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15
Q

Glucose

A

Requires no breakdown to cross lumen –> interstitial space

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16
Q

Luminal hydrolysis

A

Protein to aa to tx lumen –> interstitial space

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17
Q

Diasaccharides hydrolyzed at brush boarder from oilgomers to monomers

A

Sucrose –> glucose + fructose for transport

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18
Q

Example of luminal hydrolysis followed by intracellular resynthesis

A

Triacylglycerol –> glycerol/FA–> cross brush border –> re-essemble TAG–> cross to interstitial

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19
Q

Carb Metabolism: Membrane Digestion (step 2) – location

A

Enzymes are integral membrane proteins bound to apical membrane of intestinal epithelial cells

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20
Q

Lactose

A

Enzyme: Lactase
Transport: SGLT1
Monomers: Glucose + Galactose

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21
Q

Maltose

A

Enzyme: Glucoamylase (maltase)
Transport: SGLT1
Monomers: Glucoses

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22
Q

Sucrose & Maltose

A

Enzyme: Sucarase (Sucrose –>glucose+fructose)-isomaltase (maltose –> glucose)
Transport: SGLT1 & GLUT5
Monomers: Glucose + Fructose (sucrose) & Glucose + Glucose (maltose)

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23
Q

Salivary gland
-Product
-Substrate
-Stimulator

A
  1. Salivary a-amylase
  2. Starch (amylose & amylopectin)
  3. Food stimuli (PNS)
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24
Q

Pancreas Acinar cells
-Product
-Substrate
-Stimulator

A
  1. Pancreatic a-amylase
  2. Starch (amylose & amylopectin)
  3. Choleocystokinin (CCK) –> stim a-amuylase secreation (acinar cells)
25
Q

SGLT1

A

Na+ coupled transporter

Mediates: uptake of GLUCOSE & GALACTOSE (lumen->enterocyte)

Secondary active tx

26
Q

GLUT5

A

Mediates FACILITATED diffusion of FRUCTOSE into enterocyte

27
Q

GLUT2

A

Mediates the FACILITATED diffusion of GLUCOSE, FRUCTOSE, GALACTOSE

Basolateral –> interstitial space (circulation)

28
Q

Impacts glucose in plasma & H2 in the breath

A

Lactase deficiency

29
Q

3 ways to digest proteins

A
  1. Luminal peptidases
  2. Brush boarder peptidases
  3. Cytosolic peptidases
30
Q

Pancreas secretes 5 proteases as proenzyme (activate in small intestine work at slightly alkaline pH)

A

Endopeptidases: TRYPSIN, CHYMOTRYPSIN, ELASTASE

Exopeptidases: CARBOXYPEPTIDASE A & B

31
Q

3 endopeptidases (trypsin, chymotrpysin, elastase)

A

Disassemble proteins into oligopeptides (<6 aa)

32
Q

Exopeptidases (carboxypeptidase A & B)

A

Cleave off single aa from oligopeptides

33
Q

Proteases also xxxx –> leads to rapid decrease in luminal activity once enzymes are active

A

DIGEST EACH OTHER

34
Q

Luminal peptidases

A

Secreted by stomach (pepsin) and pancreas (tyrpsin, chymotrypsin, carbozypeptidases)

Break proteins into smaller oligopeptides in lumen of stomach/small intestine

35
Q

Brush border peptidases

A

Located apical membrane enterocytes

Hydrolyze oligopeptides into aa and di/tripeptides for absorption

36
Q

Cytosolic peptidases

A

INSIDE enterocytes

Further hydrolyze absorbed dipeptides and tripeptides into aa – transported into bloodstream

37
Q

Trypsin

A

Pancreatic protease

Secreted as trypsinogen

Activates other zymogens

Digests proteins to peptides and aa

38
Q

Chymotrypsin

A

Pancreatic protease

Secreted as chymotrypsinogen

Cleaves aromatic aa within peptide chain

39
Q

Carboxypeptidase A

A

Pancreatic protease

Secreted as procarboxypeptidase A

Cleaves hydrophobic aa from the C-terminus

40
Q

Carboxypeptidase B

A

Pancreatic protease

Secreted as procarboxypeptidase B

Cleaves basic aa (lysine, arginine) C-terminus

41
Q

Apical absorption enterocyte

  1. Dipeptides, tripeptides, tetrapeptides
  2. AA
A
  1. Occurs w/ H+ driven transporter
  2. occurs with Na+-AA co-transporter
42
Q

Lipase

A

Triglyceride –> monoglyceride + Fatty Acid

43
Q

Cholesterol ester hydrolase

A

Cholesterol ester –> Cholesterol + Fatty Acid

44
Q

Phospholipase A2

A

Phospholipid –> Lysolecithin + Fatty Acid

45
Q

Triacylglycerol (TAGs)

Most of lipids in diet

A

3 Fatty Acids to a glycerol backbone

46
Q

Other lipids in diet (not TAGs)

A

Phospholipids
Cholesterols
Free Fatty Acids

47
Q

Lingual Lipase

A

Not a sig role

Stim: fat in food – sent to stomach

Produce: Fatty Acid & Diacylglycerols (DAG)

Can’t break long chain fatty acids

48
Q

Gastric Lipase

A

Produced by chief cells

Stim: Gastrin from G cells

Resistant to PEPSIN in acidic environment

Produce: Fatty Acid & Diacylglycerols (DAG)

Can’t break long chain fatty acids

49
Q

Long Chain Fatty Acids

A

Require emulsification by bile salts in small intestine

Further breakdown by pancreatic lipase

50
Q

Fat digestion

A

Initiated in stomach
Completed in duodenum/jejunum

51
Q

CCK (Cholecystokinin)

A

Release in response to FA enter duodenum

Stim: bile release and pancreatic enzymes

52
Q

GIP (gastric inhibitory polypeptide)

A

Released by duodenal mucosa in response to FA

Helps regulate gastric emptying

53
Q

Pancreatic lipase

A

MAJOR enzyme for TAG digestion in small intestine

requires colipase (cofactor for pancreatic lipase)

Hydrolyzes TAGs into monoacylglycerols (MAGs x2), free fatty acids (FFAs)

54
Q

Bile Salts

A

Emulsify fat droplets – increase surface area for enzyme activity

Facilitate the formation of micelles (transport digestion products MAGs/FFAs/Cholesterol/fat-soluble vita) to brush border –> absorb

Recycled via enterohepatic circulation (REUSE)

55
Q

Micelles

A

Diffuse through water layer @ intestinal brush border –> efficient lipid absorption enterocytes

Lipid components absorbed by specific transporters

56
Q

Short chain FA (SCFA)
Med chain FA (MCFA)

A

Diffuse across intestinal epithelium and enter the portal circulation

57
Q

Long chain FA (LCFA)
MAGs
Lysophospholipids
Cholesterols

A

Re-esterified, incorporated into chylomicrons and exocytosed

Chylomicrons so large can ONLY access lymphatic vessels

58
Q

Absorption of Vitamin B12 (cobalamin)

A

Stomach: B12 binds to heptocorrin

Small intestine: binds to intrinsic factor (IF) —> absorbed endocytosis by enterocytes in ILEUM

59
Q

Vitamin B12

A

Required for conversion of homocysteine–>methionine

GEMS (20 decks)

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