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GI II > HECKdigestion and absorption of carbs and proteins > Flashcards

HECKdigestion and absorption of carbs and proteins Flashcards

1
Q

What are nondigestable polysaccharides

A

fiber like pectin and cellulose

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2
Q

What are types of digestable polysaccharides

A

starch, glycogen, amylose and amylopectin

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3
Q

Majority of consumed digestible peptides are what

A

starch primarily from plants

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4
Q

What is the main source of glycogen that we consume

A

animals

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5
Q

What is the difference between amylose and amyloopectin

A

amylose is a straight polymer and amylopectin is branched

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6
Q

What are the two main dietary oligosaccharides and what are they digested into

A

sucrose: glucose and fructose
lactose: glucose and galactose

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7
Q

What are the main dietary monosaccharides

A

glucose and fructose

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8
Q

What type of carbohydrate can the intestine absorbe

A

monosaccharides

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9
Q

What are the 2 steps in the digestive process

A

intraluminal hydrolysis

and membrane digestion

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10
Q

What occurs in intraluminal hydrolysis

A

enzymatic digestion in the lime- alpha amylase

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11
Q

What is the primary alpha maylase that we use? secondary?

A

salivary amylase

secondary: pancreatic amylase

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12
Q

what activates alpha amylase and what inactivates the salivary amylase

A

secreted in active form to initiate starch digestion

inactivated by gastric acid

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13
Q

What is the role of pancreatic amylase and what stimulate the release

A

completes stach digestion in lumen of SI

stimulated by CCK

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14
Q

The pancreatic amylases cannot digest what

A

terminal linkages and branch points 1,6 on saccharides

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15
Q

Describe where membrane digestion takes place and the key enzymes

A

brush border enzymes- integral membrane proteins mainly in the proximal jejunum and none in the colon
lactase, glucoamylase and sucrase-isomaltase

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16
Q

What is the role of lactase

A

digests lactose into glucose and galactose

expression decreases after weaning in the infant

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17
Q

what is the role of sucrase-isomaltase

A

sucrase splits sucrose

isomaltase splits the branch points

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18
Q

What 3 monosaccharides are readily absorbed in SI

A

glucose, galactose and fructose

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19
Q

What is the SGLT1

A

Na/glucose(galactose) transporter responsible for nutritional uptake
secondary active transcellular

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20
Q

What drives the SGLT1

A

intracellular Na from activity of the NaKATPase

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21
Q

What is the GLUT5 transporter and where is it

A

Only found in jejunum on apical membrane

responsible for fructose uptake and works based on fructose [ ] aka facilitated diffusion

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22
Q

Where is the GLUT2 transporter and where is it

A

on basolateral membrane to transfer all monosccharides into interstitium based on [ ] so facilitated diffusion

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23
Q

The best way to describe the lactase downregulation after weaning inheritance

A

epigenetic modification

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24
Q

What are symptoms of a lactase deficiency or lactose intolerance and determined by?

A

cramps, diarrhea, flatulence

determined by rate of peristalsis and gastric emptying and colonic bacteria

25
Q

What does colonic bacteria have to do with lactase deficiencies

A

metabolize undigested lactose into:
smaller chains to induce diarrhea
CO2–>flatulence
H2–>released in breath

26
Q

What is a good way to test for lactase deficiency

A

Hydrogen breath test

27
Q

What can cause a glucose-glactose malabsorption problem

A

single aa substitute missense in SGLT1 gene inhibiting its function

28
Q

What are the symptoms of glucose-glactose malabsorption and Tx

A

osmotic diarrhea

Tx: fructose based diet

29
Q

What muse proteins be digested into to be absorbed

A

oligopeptides and aa

30
Q

What are the different luminal protease pathways for protein digestion

A

when they are secreted by stomach and pancreas and hydrolyze into peptides and aa
when they hydrolyze peptides to oligopeptides which are taken up in enterocyte and hydrolyzed intracell to aa
when they hydrolyze peptides into oligopeptides and taken up by enterocyte then directly moved to interstitium

31
Q

What is the other bath of protein digestion that does not involve luminal proteases

A

brush border proteases that hydrolyze peptides to aa

32
Q

50% of protein entering SI comes from what

A

food

other 50 sloughed cells

33
Q

What is the difference with endopeptidases and exopeptidases

A

endopeptidase cleave internal sequences and result in oligopeptides
exopeptidases cleave at terminal sequence (amino or carboxyl) and release single aa

34
Q

What state are proteases in when secreted from stomach and what are they

A

zymogens: pepsinogen

35
Q

What activates pepsinogen

A

pH dependent - very acidic

irreversible inactivated at pH7

36
Q

What type of peptidase is pepsinogen and what releases it

A

endopeptidase secreted from chief cell

37
Q

What state are pancreatic proteases secreted in and give examples

A

zymogens

Trypsinogen, chymotrypsinogen, proelastase and procarboxypeptidase A

38
Q

What activates tyrpsinogen

A

trypsin secreted by jejunal brush border

39
Q

What else does trypsin activate

A

chymotrypsinogen, proelastase and procarboxypeptidase A and B

40
Q

What pancreatic proteases are endopeptidases

A

trypsinogen, chymotrypsinogen, proelastase

41
Q

What pancreatic proteases are exopeptidases

A

Procarboxypeptidaase A and B

42
Q

Why is there such a large number of brush border peptidases in the SI

A

each peptidase recognizes only some peptide bonds on larger oligopeptides

43
Q

What do cytoplasmic peptidases cleave

A

smaller dipeptides and tripeptides

44
Q

What is the PepT1 transporter

A

transports oligopeptides across lumen

45
Q

When does whole prtein absorption take place

A

first 6 mo in neonate

46
Q

What is the reason for whole protein absorption in neonates

A

passive immunity from mother to chile (Ab)

47
Q

What causes closure of whol protein absorption

A

hormones

corticosteroid admin can induce this

48
Q

What cells are specifically available to allow full proteins to cross lumen barrier

A

M cells, bring to the peyers patches

49
Q

Where can full proteins cross in adults

A

still frhouth enterocytes but very rare

M cells in the peyers patches (lamina propria)

50
Q

How do M cells transport full proteins

A

package as Ag in clathrin coated vesicles and present to immunocompotent cells at basolateral side–> mucosal immunity

51
Q

What runs PepT1 transporter

A

H/oligopeptide co transporter from H/Na gradient

52
Q

What transporter allows for aa to enter blood the fastest way

A

PepT1 because active transport, higher kinetics

53
Q

What are the two main categories about single aa transporters on apical membrane

A

Na dependent transport neutral aa

Na independent transport basic aa and cysteine

54
Q

Describe the 5 types of basolateral aa single transporters

A

3 for exit that are Na independent

2 for entrance Na dependent and good for enterocyte and nutrition

55
Q

What type of inheritance is hartnup disease and cystinuria

A

both are autosomal recessive

56
Q

What is hartnup disease

A

defect in apical transport of neutral aa (Na dependent)

pellagra, cerebellar ataxia, psychiatric abnormalities

57
Q

What is cystinuria

A

defect in apical transport of basic aa and cystein (Na independent)
kidney stones

58
Q

What are the Tx for hartnup or cystinuria

A

no Tx except for dietary changes becuase each one can still transport the other type of aa

GI II (12 decks)

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