Digestion and Absorption Flashcards Preview

Jason's GI Block > Digestion and Absorption > Flashcards

Flashcards in Digestion and Absorption Deck (49):
1

2 major sites of digestion:

duodenum
upper jejunum

2

3 diasaccharides are:

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

3

3 monosaccharides:

glucose
fructose
galactose

4

a-amylase hydrolyses what?

1:4a linkages between glucose molecules

5

what happens to a-amylase at low pH?

inactivated

6

what happens to a-amylase in duodenum?

re-activated after neutral pH is achieved

7

is a-amylase active in small bowel?

not really

8

CCK from starches?

not so much.
more so from proteins and fat

9

pancreatic a-amylase secreted due to?

CCK

10

pancreatic and salivary a-amylase are ineffective at what?

breaking 1:6a linkages

11

where are 1:6a linkages broken down?

at the brush borders of mucosal enterocytes

12

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

isomaltase
sucrase
maltase

13

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

pancreatic proteases

14

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

tips of villi
duodenum/jejunum epithelium

15

glucose absorption depends on what electrolyte?

Na+

16

2 ways to enhance glucose transport:

high salt intake
enhance sweet taste receptor

17

sodium and glucose and transported together through:

SGLT1
sodium-dependent glucose transporter

18

what does GLUT5 transport? how?

fructose via facilitated diffusion into CELL

19

what does GLUT2 do?

fructose transporter into interstitium

20

where does proteins start to get digested? by what?

stomach with pepsin

21

pepsinogen activated by?

gastric acid

22

where is pepsinogen I secreted? vs. pepsinogen II

pepsinogen I: acid secreting regions
pepsinogen II: pylorus

23

pepsin hydrolyses which bonds?

between phenyalanine and tyrosine and the 2nd amino acid

24

how is pepsin inactivated?

neutral pH

25

pepsin is important in breaking down this cellular structure:

cell-cell adhesions

26

CCK triggers release of what?

pancreatic proteases in proenzyme form

27

How is pancreatic juice first activated?

via enterokinase

28

enterokinase does what?

activates proenzymes to active form: eg. trysinogen>trypsin

29

What does trypsin, elastase, chymotrypsin digest? products?

they are endopeptidases
interior bonds of proteins
make short polypeptides

30

what digests the short polypeptides after the endopeptidases?

pancreatic carboxypeptidases

31

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

1. aminopeptidases
2. dipeptidases
3. carboxypeptidases
4. endopeptidases

32

can only free amino acids be transported into enterocytes?

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

33

one universal amino acid transporter?

nope, at least 7 that we know of

34

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

Na+
Cl-

35

what happens to AAs and sugars once in the cells?

into interstitium>circulation>portal vein>liver

36

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

mouth
lingual lipase
just for taste

37

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

not really
probably triggers CCK from duodenum

38

how is lipase activated? where?

duodenum via colipase

39

how is colipase activated?

via trypsin via CCK

40

how is cholesterol esterase activated?

by bile

41

what does emulsify mean?

make into very small droplets (micelles) for better mixing

42

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

need VIGOROUS MIXING!

43

fats absorbed where on villi? how?

tips of villi
micelles allow the lipids to dissolve through membrane

44

what happens to fat after it enters the cell?

reformed into triglycerides in smooth ER

45

how are triglycerides packaged in enterocytes?

coated with apo-lipoproteins and form chylomicrons

46

how are chylomicrons transported?

lymphatics

47

do all fats go into lymphatics?

shorter 10-12 carbon fatty acids diffuse to venules directly

48

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

fermentation of fibre by our microbiota

49

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

distal small bowel
proximal part of colon