Digestion and Absorption

Question 1

2 major sites of digestion:

Answer 1

duodenum

upper jejunum

Question 2

3 diasaccharides are:

Answer 2

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

Question 3

3 monosaccharides:

Answer 3

glucose
fructose
galactose

Question 4

a-amylase hydrolyses what?

Answer 4

1:4a linkages between glucose molecules

Question 5

what happens to a-amylase at low pH?

Answer 5

inactivated

Question 6

what happens to a-amylase in duodenum?

Answer 6

re-activated after neutral pH is achieved

Question 7

is a-amylase active in small bowel?

Answer 7

not really

Question 8

CCK from starches?

Answer 8

not so much.

more so from proteins and fat

Question 9

pancreatic a-amylase secreted due to?

Answer 9

CCK

Question 10

pancreatic and salivary a-amylase are ineffective at what?

Answer 10

breaking 1:6a linkages

Question 11

where are 1:6a linkages broken down?

Answer 11

at the brush borders of mucosal enterocytes

Question 12

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

Answer 12

isomaltase
sucrase
maltase

Question 13

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

Answer 13

pancreatic proteases

Question 14

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

Answer 14

tips of villi

duodenum/jejunum epithelium

Question 15

glucose absorption depends on what electrolyte?

Answer 15

Na+

Question 16

2 ways to enhance glucose transport:

Answer 16

high salt intake

enhance sweet taste receptor

Question 17

sodium and glucose and transported together through:

Answer 17

SGLT1

sodium-dependent glucose transporter

Question 18

what does GLUT5 transport? how?

Answer 18

fructose via facilitated diffusion into CELL

Question 19

what does GLUT2 do?

Answer 19

fructose transporter into interstitium

Question 20

where does proteins start to get digested? by what?

Answer 20

stomach with pepsin

Question 21

pepsinogen activated by?

Answer 21

gastric acid

Question 22

where is pepsinogen I secreted? vs. pepsinogen II

Answer 22

pepsinogen I: acid secreting regions

pepsinogen II: pylorus

Question 23

pepsin hydrolyses which bonds?

Answer 23

between phenyalanine and tyrosine and the 2nd amino acid

Question 24

how is pepsin inactivated?

Answer 24

neutral pH

Question 25

pepsin is important in breaking down this cellular structure:

Answer 25

cell-cell adhesions

Question 26

CCK triggers release of what?

Answer 26

pancreatic proteases in proenzyme form

Question 27

How is pancreatic juice first activated?

Answer 27

via enterokinase

Question 28

enterokinase does what?

Answer 28

activates proenzymes to active form: eg. trysinogen>trypsin

Question 29

What does trypsin, elastase, chymotrypsin digest? products?

Answer 29

they are endopeptidases interior bonds of proteins make short polypeptides

Question 30

what digests the short polypeptides after the endopeptidases?

Answer 30

pancreatic carboxypeptidases

Question 31

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

Answer 31

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

Question 32

can only free amino acids be transported into enterocytes?

Answer 32

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

Question 33

one universal amino acid transporter?

Answer 33

nope, at least 7 that we know of

Question 34

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

Answer 34

Na+ | Cl-

Question 35

what happens to AAs and sugars once in the cells?

Answer 35

into interstitium>circulation>portal vein>liver

Question 36

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

Answer 36

mouth lingual lipase just for taste

Question 37

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

Answer 37

not really | probably triggers CCK from duodenum

Question 38

how is lipase activated? where?

Answer 38

duodenum via colipase

Question 39

how is colipase activated?

Answer 39

via trypsin via CCK

Question 40

how is cholesterol esterase activated?

Answer 40

by bile

Question 41

what does emulsify mean?

Answer 41

make into very small droplets (micelles) for better mixing

Question 42

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

Answer 42

need VIGOROUS MIXING!

Question 43

fats absorbed where on villi? how?

Answer 43

tips of villi | micelles allow the lipids to dissolve through membrane

Question 44

what happens to fat after it enters the cell?

Answer 44

reformed into triglycerides in smooth ER

Question 45

how are triglycerides packaged in enterocytes?

Answer 45

coated with apo-lipoproteins and form chylomicrons

Question 46

how are chylomicrons transported?

Answer 46

lymphatics

Question 47

do all fats go into lymphatics?

Answer 47

shorter 10-12 carbon fatty acids diffuse to venules directly

Question 48

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

Answer 48

fermentation of fibre by our microbiota

Question 49

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

Answer 49

distal small bowel | proximal part of colon