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Jason's GI Block > Digestion and Absorption > Flashcards

Digestion and Absorption Flashcards

1
Q

2 major sites of digestion:

A

duodenum

upper jejunum

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2
Q

3 diasaccharides are:

A

lactose (G-Ga)
sucrose (G-F)
maltose (G-G)

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3
Q

3 monosaccharides:

A

glucose
fructose
galactose

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4
Q

a-amylase hydrolyses what?

A

1:4a linkages between glucose molecules

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5
Q

what happens to a-amylase at low pH?

A

inactivated

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6
Q

what happens to a-amylase in duodenum?

A

re-activated after neutral pH is achieved

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7
Q

is a-amylase active in small bowel?

A

not really

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8
Q

CCK from starches?

A

not so much.

more so from proteins and fat

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9
Q

pancreatic a-amylase secreted due to?

A

CCK

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10
Q

pancreatic and salivary a-amylase are ineffective at what?

A

breaking 1:6a linkages

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11
Q

where are 1:6a linkages broken down?

A

at the brush borders of mucosal enterocytes

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12
Q

3 enzymes that break 1:6a linkages at brush border?

A

isomaltase
sucrase
maltase

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13
Q

Maltase and sucrase and made as a single large glycoprotein in the brush border membrane, how do you activate it?

A

pancreatic proteases

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14
Q

where on the villi and the GI are glucose and fructose absorbed?

A

tips of villi

duodenum/jejunum epithelium

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15
Q

glucose absorption depends on what electrolyte?

A

Na+

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16
Q

2 ways to enhance glucose transport:

A

high salt intake

enhance sweet taste receptor

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17
Q

sodium and glucose and transported together through:

A

SGLT1

sodium-dependent glucose transporter

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18
Q

what does GLUT5 transport? how?

A

fructose via facilitated diffusion into CELL

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19
Q

what does GLUT2 do?

A

fructose transporter into interstitium

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20
Q

where does proteins start to get digested? by what?

A

stomach with pepsin

21
Q

pepsinogen activated by?

A

gastric acid

22
Q

where is pepsinogen I secreted? vs. pepsinogen II

A

pepsinogen I: acid secreting regions

pepsinogen II: pylorus

23
Q

pepsin hydrolyses which bonds?

A

between phenyalanine and tyrosine and the 2nd amino acid

24
Q

how is pepsin inactivated?

A

neutral pH

25
Q

pepsin is important in breaking down this cellular structure:

A

cell-cell adhesions

26
Q

CCK triggers release of what?

A

pancreatic proteases in proenzyme form

27
Q

How is pancreatic juice first activated?

A

via enterokinase

28
Q

enterokinase does what?

A

activates proenzymes to active form: eg. trysinogen>trypsin

29
Q

What does trypsin, elastase, chymotrypsin digest? products?

A

they are endopeptidases
interior bonds of proteins
make short polypeptides

30
Q

what digests the short polypeptides after the endopeptidases?

A

pancreatic carboxypeptidases

31
Q

at the brush border there are a mix of 4 peptidases, they are:

A
  1. aminopeptidases
  2. dipeptidases
  3. carboxypeptidases
  4. endopeptidases
32
Q

can only free amino acids be transported into enterocytes?

A

nope, di- tri- can be transported and broken by enterocyte small peptidases

33
Q

one universal amino acid transporter?

A

nope, at least 7 that we know of

34
Q

what do you need to co-transport for Amino acids into enterocytes

A

Na+

Cl-

35
Q

what happens to AAs and sugars once in the cells?

A

into interstitium>circulation>portal vein>liver

36
Q

where does fat digestion start? with what? is it effective?

A

mouth
lingual lipase
just for taste

37
Q

gastric lipase big role in digestion? what’s it for?

A

not really

probably triggers CCK from duodenum

38
Q

how is lipase activated? where?

A

duodenum via colipase

39
Q

how is colipase activated?

A

via trypsin via CCK

40
Q

how is cholesterol esterase activated?

A

by bile

41
Q

what does emulsify mean?

A

make into very small droplets (micelles) for better mixing

42
Q

just add bile and lecithin to your chyme and you’re good right?

A

need VIGOROUS MIXING!

43
Q

fats absorbed where on villi? how?

A

tips of villi

micelles allow the lipids to dissolve through membrane

44
Q

what happens to fat after it enters the cell?

A

reformed into triglycerides in smooth ER

45
Q

how are triglycerides packaged in enterocytes?

A

coated with apo-lipoproteins and form chylomicrons

46
Q

how are chylomicrons transported?

A

lymphatics

47
Q

do all fats go into lymphatics?

A

shorter 10-12 carbon fatty acids diffuse to venules directly

48
Q

how are short chain fatty acids made in the proximal colon? how?

A

fermentation of fibre by our microbiota

49
Q

where are the short chain fatty acids made in the proximal colon absorbed?

A

distal small bowel

proximal part of colon

Jason's GI Block (32 decks)

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