3.01 GI Nutrtion

Question 1

What substance does not need digestion and is directly absorbed into intestinal lumen?

Answer 1

Glucose

Question 2

Where does the greatest absorption of carbs, proteins, and lipids in small intestine take place?

Answer 2

Duodenum

Question 3

Where is Ca+, Fe, and folate actively absorbed?

Answer 3

Duodenum

Question 4

Where are bile acids absorbed in small intestine?

Answer 4

Throughout entire BUT ACTIVELY only at ILEUM*

Question 5

Where is Vit B12 absorbed ?

Answer 5

Ileum

Question 6

What carbs are dircetly absorbed by the small intestine?

Answer 6

Glucose, fructose, galactose (monosaccharides)

Question 7

What initially breakdown carbohydrates aka starch?

Answer 7

A-amylase (acinar cells @ salivary glands + pancreas)

Question 8

How are the initial oligosaccharides of amylose and amylopectin (starch) broken down?

Answer 8

A- amylase via intralumenal hydrolysis

Question 9

What digests oligosaccharides further into monosaccharides?

Answer 9

Brush border disaccharidases

Question 10

Where are the brush border dissachridases?

Answer 10

Integral membrane proteins of intestinal epithelial cells (apical side)

Question 11

What are the oligosaccharidases?

Answer 11

Lactase
Glucoamylase (aka Maltase)
Sucrose-isomaltase

Question 12

Lactase substrates and products?

Answer 12

Lactose —> glucose + galactose

Question 13

Glucoamylase substrate and products?

Answer 13

Maltose —> glucose

Question 14

Sucrase-isomaltase substrates and products?

Answer 14

Sucrose — > glucose + fructose

Maltose —> glucose

Question 15

Na+ coupled transporter that mediates uptake of glucose or galactose from lumen on apical membrane?

Answer 15

SGLT1

Question 16

What kind of transport is SGLT1?

Answer 16

Secondary active transport

Question 17

Channel that mediates diffusion of fructose into enterocyte?

Answer 17

GLUT5

Question 18

Channel that mediates facilitated diffusion of glucose, fructose, or galactose across BL membrane into interstitial space —> circulation?

Answer 18

GLUT2

Question 19

Where are oligosaccharidases generally located in the GI tract/

Answer 19

Small intestine (should not be at the large intestine)

Question 20

Lactase deficiency impacts what?

Answer 20

Glucose in plasma and H2 in breath

Question 21

What will you notice in adults with a lactase deficiency?

Answer 21

Glucose levels should be normal but you will notice a higher than normal [H2 ]in their breath

Question 22

What/Where are the 3 ways/peptidases that breakdown protein?

Answer 22

Luminal peptidases
Brush border peptidases
Cytosolic peptidases

Question 23

What must proteins be digested into before they are taken up by enterocytes?

Answer 23

Oligopeptides and AA

Question 24

Where are luminal peptidases secreted and where so they work?

Answer 24

Secreted by stomach and pancrease
(Pepsin; trypsin, chemo trypsin, carboxypeptidases)
Broken down into stomach and small intestine

Question 25

What do brush border peptidases hydrolyze at apical membrane of enterocytes?

Answer 25

Oligopeptides —> AA and di/tripeptides

Question 26

Where are cytosolic peptodases found?

Answer 26

Inside enterocytes Di/tripeptidases —> AA to blood

Question 27

What are the 5 Inactivated proenzymes/zymogens secreted by the pancreas ? Endo vs. Exo?

Answer 27

(ENDO) Trypsin Chymotrypsin Elastase (EXO) Carboxypeptidase A Carboxypeptidase B

Question 28

What hydrolyses internal peptide bonds in proteins to make Oligopeptides (chains <6)?

Answer 28

Endopeptidases

Question 29

What cleaves single AA from Carboxyl end of Oligopeptides?

Answer 29

Exopeptidases

Question 30

What exopeptidase prefers hydrophobic AA?

Answer 30

Carboxypeptidase A

Question 31

What exopeptidase targets basic AA like Lys and Arg?

Answer 31

Carboxypeptidase B

Question 32

Of the ENDOpeptidases which one produces basic Oligopeptides?

Answer 32

Trypsin (onto Carboxypeptidase B next!)

Question 33

What converts the inactive pancreatic zymogens to its active form?

Answer 33

Enterokinases

Question 34

What enzyme is essential for kick starting the breakdown of proteins by activating a cascade to activate other pro enzymes?

Answer 34

Trypsin activation cascade Trypsinogen —> trypsin —> cascade)

Question 35

What actives protein digestion in the stomach under acidic conditions?

Answer 35

Pepsin

Question 36

What is activated in the small intestine and works at slightly more alkaline pH than teh stomach?

Answer 36

Pancreatic proteases (trypsinogen, chymotrypsinogen, procarboxypeptidase A & B)

Question 37

Where are amino acids cleaved from Oligopeptides with carboxypeptidases?

Answer 37

C-terminus

Question 38

What cleaves aromatic AA writhing peptide chains?

Answer 38

Chymotrypsin

Question 39

What happens to protein digestion if patients have a total gastrectomies or pernicious anemia?

Answer 39

Protein digestion and absorption remain intact But will have B12 deficiency

Question 40

How are small Oligopeptides absorbed into enterocytes on the apical membrane?

Answer 40

H+/oligopeptide cotransporter (PepT1)

Question 41

How do AA from cytoplasmic hydrolysis exit the enterocyte (via BL membrane) ?

Answer 41

Na+ independent AA transporter

Question 42

How does AA enter the enterocyte from the apical side?

Answer 42

It needs a Na+ channel (dependent)

Question 43

What are the lipase sub and products?

Answer 43

Triglyceride —> (2) FA + monoglyceride

Question 44

What are the cholesterol ester hydrolase sub and products?

Answer 44

Cholesterol ester —> cholesterol + FA

Question 45

What are the phospholipids A2 sub and products?

Answer 45

Phospholipid —> Lysolecithin + FA

Question 46

What is the major form of dietary lipid?

Answer 46

TAG (triacylglycerols)

Question 47

What is the TAG structure?

Answer 47

(3) FA chains Esterified to a glycerol backbone

Question 48

What are other forms of dietary lipids aside form TAGs?

Answer 48

Phospholipids, cholesterol, free FA

Question 49

What initiates lipid digestion?

Answer 49

Lingual lipase (not significant) @ mouth sent to stomach + Gastric lipase (partial digestion) @ G cells gastrin

Question 50

What is gastric lipase resistant to in an acidic environment?

Answer 50

Pepsin

Question 51

What is a required to breakdown LCFA (long chain fatty acids) when lingual lipase and gastric lipase can’t finish the job?

Answer 51

Emulsification by bile salts @ small intestine + Pancreatic lipase

Question 52

What are key hormones to regulate lipid digestion?

Answer 52

CCK and GIP

Question 53

What is release by duodenal mucosa in responses to FA to help regulate gastric emptying?

Answer 53

GIP (gastric inhib polypeptide)

Question 54

What is released in response to FA entering duodenum?

Answer 54

CCK (cholecystokinin)

Question 55

What does CCK do?

Answer 55

Stimulate bile salt release and pancreatic enzyme secretion

Question 56

What is the pancreatic lipase co-factor?

Answer 56

Colipase

Question 57

What is the major enzyme needed for TAG digestion in the small intestine?

Answer 57

Pancreatic lipase

Question 58

What is are the pancreatic lipase sub and hydrolyzed products?

Answer 58

TAG —> 2 MAGs + FFAs (2 monoacylglycerols + free fatty acids)

Question 59

What do bile salts do?

Answer 59

Emulsify fat droplets to increase surface area and form micelles that transport digestion products to brush border for absorption

Question 60

How are bile salts recycled?

Answer 60

Enterohepatic circulation

Question 61

How are lipid digestion components taken up by enterocytes?

Answer 61

Direct diffusion or specific transporters

Question 62

What helps solubulize lipid digestion products allowing them to approach the intestinal epithelium?

Answer 62

Mixed Micelles

Question 63

What are micelles made up of?

Answer 63

Bile salts, fatty acids, 2 MAGs, cholesterol, and fat soluble vitamins

Question 64

What can diffuse directly across the intestinal epithelium and enter the portal circulation?

Answer 64

SCFA and MCFA (medium)

Question 65

LCFAs, 2-MAGs, lysophopholipids, and cholesterol need what in order to enter enterocytes?

Answer 65

FATP (FA transport proteins)

Question 66

What happens to LCFAs, 2-MAGs, and cholesterol once WITHIN enterocytes?

Answer 66

Re-esterification into TAG and Cholesterol esters OR Incorporated into chylomicrons

Question 67

What do chylomicrons do once they are created in the enterocytes?

Answer 67

Exocytosis into lymphatic vessels

Question 68

What does Vitamin B12 bind to in the stomach?

Answer 68

Haptocorrin

Question 69

What needs to happen to B12-haptocorrin in order for it to enter the Ilium (absorption) ?

Answer 69

Bind to IF

Question 70

What is B12 found in diet wise?

Answer 70

Animal products Meat, fish, shellfish, eggs, milk

Question 71

Who’s at risk for a dietary cobalamin deficiency?

Answer 71

Strict vegetarians