Digestion 4: Digestion & Absorption Flashcards Preview

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Flashcards in Digestion 4: Digestion & Absorption Deck (79):
1

what are the nutrients we get from diet?

- carbs
- fat
- protein
- water, electrolytes, vitamins

2

what are the nutrients absorbed by the small intestines?

- monosaccharides
- fatty acids
- monoglycerides
- cholesterol
- AA
- water, vitamins, electrolytes

3

what type of transport is endocytosis or exocytosis?

transcytosis

4

function of sucrase

sucrose → glucose + fructose

5

function of maltase

maltose → glucose + glucose

6

function of lactase

lactose → glucose + galactose

7

function of amylase

starch, glycogen → disaccharides

8

2 ways in which shorter peptide chains can be formed

1. endopeptidase → shorter peptide chains
2. exopeptidase (aminopeptidase & carboxypeptidase) → digest peptide chains from either end to release AA

9

what is needed when peptide chains are broken?

H2O (hydrolysis)

10

does body make more aminopeptidase or carboxypeptidase

carboxypeptidase

11

function of lipase

triglyceride → monoglyceride + FFA

12

what are the fats that we eat? What is the main one?

- triglycerides (90%)
- phospholipids
- cholesterol

13

how does monosaccharides get through epithelial cells in small intestines?

enter: facilitated diffusion & co-transport

exit: facilitated diffusion

14

how does fat get through epithelial cells in small intestines?

enter: diffusion

exit: exocytosis as chylomicrons

15

how does AA and short peptides get through epithelial cells in small intestines?

enter: facilitated diffusion & co-transport

exit: facilitated diffusion & co-transport

16

brush-border enzyme for AA?

dipeptidases

17

which macronutrient is not digested in the stomach?

lipids
(carbs get some digestion from leftover salivary amylase)

18

digestion of carbs at the small intestines

1. pancreatic a-amylase
2. lactase, maltase, sucrase

19

digestion of proteins at the small intestines

1. trypsin, chymotrypsin, elastase, carboxypeptidase
2. dipeptidase

20

digestion of fat at the small intestines

bile acids;
pancreatic lipase

21

function of salivary amylase

starch → MALTOSE + maltotriose + dextrin

22

__% of starch digestion occurs in mouth, __% occur in stomach

5;
35

23

about ___ min after swallowing, salivary amylase becomes inactivated by low stomach pH

30-40

24

function of pancreatic amylase

starch → MALTOSE + maltotriose + dextrin

25

even though pancreatic amylase == salivary amylase, it is more potent because...

- food is smaller at small intestines, so there is more SA for it to act on
- food stays in intestines longer

26

___ is important for pancreatic amylase activity because...

bicarb;
need to neutralize acidic chyme so pancreatic amylase is at the optimal pH

27

how to explain the symptoms of lactose intolerance?

diarrhea: lactose in large intestines draw water into lumen

gas: bacteria in large intestines use lactose as food → gas is byproduct of fermentation

cramps: build up of CO2 → distention → peristalsis

28

what is used to absorb monosaccharides?

GLUT-5 & SGLT (sodium glucose linked transporter)

29

brush-border enzymes used to digest saccharides

- maltase-glucoamylase
- dextrinase
- sucrase
- lactase

30

where are brushborder enzymes located?

embedded in walls of small intestines

31

which transporters are used to absorb glucose, galactose, and fructuse?

SGLT: glucose & galactose (exit by facillitated diffusion or GLUT2)
GLUT5: fructose (exits the cell using GLUT2)

32

there is competition for absorption of the different monosaccharides. What is the order?

absorbed first → last:
galactose > glucose > fructose

33

function of pepsin

protein → peptides + AA
- endopeptidase
- cleaves at aromatic AA (FYW)

34

pancreas secretes ____ for protein digestion

zymogens
- chymotrypsinogen
- procarboxypeptidase
- procolipase
- prophospholipase

35

function of enterokinase

activate trypsinogen → trypsin

36

how are zymogens activated?

1. enterokinases activate trypsinogen → trypsin
2. trypsin activates rest of zymogens

37

activated pancreatic enzymes for protein digestion

- chymotrypsin
- carboxypeptidase
- colipase
- phospholipase

38

Pancreatitis

if trypsinogen is activated too early → digestion of the pancreas

39

how does the pancreas protect itself from being digested by protein-digesting enzymes?

1. separate trypsinogen from lysozymes in cytoplasm
2. trypsin can digest itself
3. pancreas can make trypsin inhibitor (secreted if trypsin present in pancreas)

40

___ and ___ are endopeptidases, while ___ removes AA from C-term

trypsin & chymotrypsin;
carboxypeptidase

41

brushborder enzymes for proteins

- aminopeptidase (cleave from N-term)
- dipeptidase (dipeptide → AA)

42

where are aminopeptidase & dipeptidase located?

embedded in brushborder

43

which forms of protein can be absorbed?

1. di- & tripeptides
2. AA
3. small peptides

44

absorption of di- & tripeptides

transporter: PepT1
- cotransport with H+ on both apical side
- exchange with H+ on basolateral side
- can be cleaved inside cell by peptidases → AA
- functionally linked to NHE to keep [H] inside the cell low

45

absorption of AA

- cotransport with Na+ on apical side
- exchange with Na+ on basolateral side
- Na/K-ATPase used to keep concentration of Na low inside cell

46

absorption of small peptides

transcytosis

47

gastric lipase is secreted by...

chief cells

48

digestion of fat in stomach

- gastric lipase
- agitation forms smaller fat droplets

49

what is 1 instance in which gastric lipase > pancreatic lipase?

ZE syndrome:
very acidic chyme means gastric lipase is in optimal environment, but pancreatic isn't

50

why is 1 symptom of ZE syndrome malnutrition?

super acidic chyme makes all pancreatic enzymes (majority of digestion for all nutrients) less effective

51

what emulsify fats?

- bile salt (from liver)
- phospholipid lecithin (from liver)

52

purpose of emulsion?

increase SA for further digestion by pancreatic lipase

53

colipase

- pancreatic lipase can't attach on emulsified fat due to bile salts
- colipase attaches bile salt on 1 end and lipase on other end → allows digestion to happen

54

micelles

- very small emulsified fat particles
- hydrophilic shell
- hydrophobic core (FFA, cholesterol, etc.)
- small enough to be soluble

55

absorption of fat

1. FFA & monoglycerides diffuse into cell
2. go to smooth ER → re-esterify back to triglycerides
3. cholesterol enters cell via NPC1L1 (energy dependent transporter) → sER
4. everything comes together at sER → packaged at Golgi → chylomicron
5. leaves cell via exocytosis → lymphatic system → thoracic duct → subclavian vein

56

ezetimibe

drug that lowers cholesterol levels by preventing absorption
- block NPC1L1 transporter

57

function of lipoprotein lipase (LPL)

TG in chylomicrons → FFA + glycerol

58

chylomicrons is made up of...

- TG (most)
- Cholesterol
- PL
- apoproteins

59

LPL can be found most abundantly in...

- capillaries associated with muscles
- adipose tissues
- capillaries associated w/ lactating boobs

60

vit B12 sources

- made by bacteria
- seafood
- meat
- milk

61

Pernicious anemia causes

- lack of intrinsic factors being secreted by parietal cells
- not enough dietary B12
- too much bac't in gut (eat up B12 before reaching ileum)

62

B12 is required for...

maturation of RBC

63

Pernicious anemia

condition where patients don't have mature RBC because Vitamin B12 is required for the maturation of RBC

64

calcium can be absorbed 2 ways...

1) paracellular
2) hormone dependent absorption

65

hormone-dependent Ca absorption

1. Ca enters cell through Ca-channel
2. Ca bind to calbindin in cell (free Ca is very bad for cell
3. when needed, Ca is released from calbindin and exits through Ca-ATPase

66

calbindin is increased by...

vit D (calcitriol)

67

how does 1,25(OH)2 vitD3 enhance Ca absorption?

1) increase Ca channels on apical membrane
2) increase amount of calbindin

68

iron is absorbed in which forms?

1) heme (easily absorbed)
2) ferrous (Fe++)

69

absorption of heme iron

transporter: HCP1 (heme carrier protein)

after getting into cell, dissociates → porphyrin + ferrous form

70

absorption of ferrous iron

transporter: DMT-1 (divalent metal transporter)
- Fe and H cotransporter

1. ferrous form + apoferritin → ferritin
2. ferritin can be used to store lots of iron inside cell until needed

71

what happens when we want to use iron bound in ferritin?

- ferrous iron transported outside by ferroportin
- ferroportin levels regulated by hepcidin

72

ferroportin regulation

- hepcidin causes internalization of ferroportin
- YES hepcidin = no ferroportin = no Fe leaving cells
- NO hepcidin = yes ferroportin = yes Fe leaving cells

73

hepcidin

hormone released by liver to regulate levels of ferroportin

74

Na+ absorption

apical membrane transporters for Na+:
- Na channel
- Na/Cl-cotransporter
- Na/H-exchanger
- Na/organic solute cotransporter

basolateral membrane transporters for Na+:
Na/K-ATPase

75

Cl- absorption

apical membrane transporters for Cl-:
- Na/Cl-cotransporter
- bicarb/Cl-exchanger

basolateral membrane transporter for Cl-:
- Cl channel

76

how does water get absorbed?

- paracellular pathway, following solute
- active transport with SGLT transporter

77

how does K+ get absorbed?

paracellular pathway, along with water

78

SGLT is only present on __ membrane

apical

79

how is water transported with SGLT?

- Na binds, then glucose/galactose
- follows glucose/galactose when it binds
- about 250 molecules moved every time