Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

GUT P&P > Digestion and defence > Flashcards

Digestion and defence Flashcards

1
Q

enterocyte turnover

A

3-7 days

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

stages of carbohydrate digestion

A
  1. salivary amylase initiates digestion, hydrolysing starch to maltose, maltotriose and alpha limit dextrin
  2. pancreatic amylase continues this process
  3. brush border dissaccharidases further hydrolyse the carbohydrates
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

four different membrane bound disaccharidases + function

A

lactase- lactose into glucose and galactose

maltase- maltose or maltotriose into glucose

sucrase- sucrose into glucose and fructose

sucrose-isomaltase- sucrase hydrolyses sucrose into glucose and fructose, isomaltase maltose and maltotriose into glucose

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

which carbohydrate isomers are absorbed?

A

D

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

where are the disaccharidases expressed?

A

apical membrane of the small intestine

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

how do carbohydrates move across the apical bilayer?

A

SGLT1- glucose and galactose across the apical membrane utilising sodium gradient

GLUT2- can be inserted

GLUT5- fructose

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

how do carbohydrates move across basolateral bilayer?

A

GLUT2

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

by which point is carbohydrate absorption completed?

A

mid jejunum

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

what happens to unabsorbed carbohydrates?

A

stimulate colonic motility and secretion, leading to cramps and diarrhea

will be present in stool

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

explain the components and actions of oral rehydration therpapies

A

contain isoosmotic solution of salt and glucose

glucose is taken up via SGLT1 alongside sodium

water follows the sodium

leading to less water loss

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

where are proteins absorbed? + what form?

A

small intestine, amino acids and peptides

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

stages of protein digestion

A
  1. pepsinogen cleaved in acidic environment to form pepsin, activated by truncation
  2. pepsin is an endopeptidase that breaks down proteins into smaller peptides in the stomach
  3. pancreatic endopeptidases further digest proteins to form oligopeptides 2-6aa and amino acids
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

two pancreatic endopeptidases

A

trypsin and chymotrypsin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

difference between trypsin and chymotrypsin

A

trypsin selects for basic amino acids, lysine and arginine

chymotrypsin selects for aromatic amino acids, phenylalanine, tryptophan and tyrosine

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

what activates trypsin?

A

enteropeptidase

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

what is enteropeptidase?

A

a serine protease enzyme produced by the cells of the duodenum that converts the zymogen trypsinogen to its active form trypsin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

what digestion occurs at the brush border?

A

oligopeptide digestion to form tri and di peptides

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

how are amino acids absorbed ?

A

by apical carriers, mostly sodium dependent with different classes- neutral, cationic and basic

then move out basolaterally via sodium independent carriers

19
Q

how are di/tripeptides absorbed?

A

absorbed by hydrogen dependent apical carrier protein PEPT-1

once within the cell, cytsolic peptidases convert the peptides to amino acids

amino acids then move out basolaterally via sodium independent transporters

20
Q

where is absorption complete by?

A

end of the jejunum

21
Q

where does the majority of lipid digestion take place?

A

small intestine

22
Q

stages of lipid digestion

A
  1. muscular movements emulsify fats with bile salts
  2. pancreatic lipase digest triglycerides to monoglycerides and free fatty acids
  3. pancreatic colipase enables lipase o bind to the emulsion
23
Q

stages of lipid absorption

A
  1. monoglycerides and free fatty acids are incorporated into micelles using bile salts from the liver
  2. micelles diffuse in the unstirred acidic later adjacent to the apical membrane
  3. components dissociate at the cell surface
  4. components are reassembled in the SER
  5. combine with apolipoproteins in the RER to form chylomicrons
  6. chylomicrons are then exported by the golgi into the lymphatic capillaries
  7. lymph drains back into the left subclavian vein via the thoracic duct or lymphatic duct
24
Q

bile composition

A

water- 97%

bile salts 0.7%

bilirubin 0.2%

fats 0.51%- cholesterol, fatty acids and lecthinin

25
Q

function of bile

A

acts like a surfactant to emulsify the lipids in food

aggregate around droplets of lipids to form micelles

26
Q

bile salt structure

A

anions, hydrophillic on one side and hydrophobic on the other

27
Q

examples of water soluble vitamins

A

thiamine, riboflavin, B12, vitamin C and folic acid

28
Q

how do water soluble vitamins become absorbed?

A

passive diffusion paracellularly or via specific sodium coupled carrier proteins transcellularly

29
Q

explain B12 absorption

A
  1. B12 binds to a specific apical receptor
  2. Protein intrinsic factor vinds to cobalamin that can then bind to the apical membrane and become internalised by an endosome
  3. endosome is degraded by a lysosome
  4. cobalamin is then packaged with a chaperone protein into a secretory vesicle for export from the cell
30
Q

absorption of fat soluble vitamins stages

A

vitamins A,D,E and K are dissolved in bile micelles and packaged into chylomicrons like fats

31
Q

stages of iron absorption

A
  1. ferric reductase enzyme on duodenal enterocyte brush border reduces Fe3+ to 2+
  2. DMT1 then transports Fe2+ into the cell. If the iron is bound to heme it is transported voa the apical heme carrier protein
  3. iron is then storred as ferritin or it is released into the body via ferroportin
32
Q

what regulates iron absorption + how?

A

hepcidin released when too much iron

post translationally represses ferroportin

33
Q

stages of calcium absorption

A
  1. calcium taken up apically
  2. binds to calbindin, a vitamin D dependent calcium binding protein, which transfers it to the ER
  3. calcium then moved to basolateral membrane
  4. three calcium pumps actively transport calcium from the body
34
Q

important regulator of calcium absorption

A

calcitriol- active form of vitamin D

35
Q

main passage for electrolytes explained

A

paracellular

tight junctions increase along the intestine

36
Q

cystic fibrosis explained

A

mutations in cystic fibrosis transmembrane conductance regulator

chloride and water ions cannot move out of the channel

does not resorb ions from sweat ducts, instead pumped into the skin

leads to excess mucus in lungs

37
Q

different defence mechanisms in the gut

A

taste, gastric acid, epithelial barrier, mucus, mucosal immune system

38
Q

explain taste defence

A

bitterness, normally toxic, prevent eating

39
Q

gastric acid defence

A

sterilises the components before entering the small bowel

denatures proteins

40
Q

intestinal mucosal barrier definition

A

property of the intestinal mucosa that protects mucosal tissues and circulatory system from exposure of pro inflammatory molecules such as microorganisms, toxins and antigens

41
Q

function of mucus

A

forms thick layer of mucin molecules that trap pathogens

42
Q

microbiota function

A

gut bacteria that can influence barrier function

43
Q

key structure in gut + function

A

peyers patches- lymphoid follicles that trap foreign particles, surveil them and destroy them

GUT P&P (5 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions