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Flashcards in Digestion and Absorption Deck (41):
1

What is the purpose of enterokinase?

It cleaves pepsinogen to pepsin

2

What enzymes come from the stomach?

pepsin

3

What enzymes come from the pancreas

amylase
trypsin
chymotrypsin
carboxypeptidase
lipase-colipase
phospholipase a
Cholesterol esterase

4

what enzymes come from intestine?

enterokinase
disaccharidases
maltase
sucrase
lactase
trehalase
isomaltase
peptidases

5

What is the most important part of the small bowel?

ileum, otherwise you can remove up to 60-70% and be fine.

6

Explain the changes of tight junctions in the small bowel as you go down

In the duodenum, the tight junctions are fairly loose.
once you get to the ileum, they are very tight.

7

What does amylase do? what type of link does it target?

Amylase digests to maltose and maltotriose.

Amylase targets 1:6 links

8

What is the most common disaccharide?

sucrose

9

How is glucose mainly absorbed: active or passive:

active

10

What are the three transporters for carbohydrate absorption? what are each's actions?

SGLT1 - two Na and Glucose/Galactose

GLUT2 - exits for glucose, galactose, and fructose (all three competing for access to glut2 to exit luminal cell)

GLUT5 - fructose absorption

11

What is the first stage of protein degradation?

pepsin (breaks peptide border), breaking them into di/tripeptides, large peptides and free amino acids

12

where is trypsin cleaved?

cleaved in the brush border by enterokinase

13

How are carboxypeptidases A and B different from the other peptidases?

They only cleave off one enzyme at a time.

14

Explain the actions of trypsinogen

Trypsinogen is cleaved by enterokinase to trypsin. Trypsin then activates more trypsin, chymotrypsin, elastase, and carboxypeptidases A and B

15

How big can protein particles be to be absorbed in the small intestine?

at most, tripeptides. do not leave the lumenal cell until they are individual amino acids

16

When there is an absence of carriers for a basic amino acid, how do we absorb them?

We absorb them as dipeptides still so we can obtain that nutrients.

17

What is hartnup's dz due to?

a lack of neutral amino acid carriers

18

what can result from hartnup's dz?

phellagra

19

What are the major three enzymes of triglyceride breakdown?

pancreatic lipase
cholesterol ester hydrolase
phospholipase A2

20

Explain the actions of pancreatic lipase (long answer)

Secreted as active substance. Breaks triglycerides, specifically on 1 and 3 arms. Yields 2 FAs and a monoglyceride.

Also acts on emulsion droplets, secreted 1:1 with colipase (not an enzyme) and binds to droplets displacing a BA, allowing PL to bind to emulsion droplet

Additionally binds to micelle to keep TG source nearby

21

What are the actions of cholesterol ester hydrolase?

specific for all links of TG
nonspecific

22

What does phospholipase A2 do?

releases FA from the 2nd carbon of glycerol

23

What type of absorption is the most calorie intense absorption?

lipid absorption

24

What does FABP do?

takes FA from the membrane to the SER, so you can maintain diffusion gradient

25

What happens once you bring the FA to the SER?

we resynthesize TG in SER, with fatty acyl CoA synthase. going from acyl coa -> DG -> TG. The lacteal then absorbs the TG

26

once the SER resynthesizes the TG, what happens?

They are taken to chylomicrons and released in the lymph by the lacteal

27

What are the four fat soluble vitamins?

ADEK

28

What do we need to absorb B12?

IF in the ileum

29

How many liters of water does the duodenum and jejunum absorb?
the ileum?
the colon?

4

3.5

1.4

30

In the colon, absorption of Cl is linked to secretion of what?

HCO3, which is why the stool water is very basic

31

What is secreted in the colon in exchange for Na?

K,

32

What are the two types of diarrhea? what are the xauses of each?

osmotic - impaired absorption, accumulation of solutes, lack of enzymes, decreased absorptive surface, precipitation of bile salts, motility

secretory - increased secretion by crypt cells, bacteria: cholera, increased secretory hormones, increased adenylate cyclase, activation of apical Cl channels

33

What protein is needed for iron absorption?

Transferrin

34

Where are satiety signals integrated?

hypothalamus

35

What are the two parts of the arcuate nucleus of the hypothalamus? what are their functions?

POMC - neurons secreting aMSH (INH intake and stimulate metabolism)

NPY - stimulated by hunger, does opposite

36

What does ghrelin do?

It stimulates food intake and the NPY and blocks the POMC

37

Source, site of action and effect of Insulin

pancreatic beta cells

hypothalamus

decrease appetitei increase metabolism

38

Source, site of action and effect of leptin

fat cells

hypothalamus, decrease NPY and increase POMC

decrease appetite and increase metabolism

39

Source, site of action and effect of cck

i-cells of duodenum

vagal afferents

decrease appetite, decreased gastric empyting

40

Source, site of action and effect of pyy

L-cells of ileum and colon

hypothalamus,

decrease appetite
increase gastric empyting

41

Source, site of action and effect of ghrelin

endocrine cells of oxyntic gland area of the stomach

hypothalamus
increase appetite
gastric emptying