Digestion and Absorption of Carbohydrates and Proteins Flashcards Preview

SF4 Exam I > Digestion and Absorption of Carbohydrates and Proteins > Flashcards

Flashcards in Digestion and Absorption of Carbohydrates and Proteins Deck (73):
1

carbohydrates must be what before being absorbed

digested into monosaccharides

2

starches are converted by what into what

salivary and pancreatic alpha-amylases
to maltose, maltotriose, and alpha-limit dextrins

3

the oligosaccharides produced by amylases are hydrolyzed into glucose by what and where

glucoamylase, isomaltase, and maltase
brush border of membrane

4

sucrose is cleaved by what into what?

sucrase
fructose and glucose

5

lactose is cleaved by what into what

lactase
glucose and galactose

6

trehalose is what (what cleaves it)

glucose dimer
trehalase

7

what is not digested by human enzymes

cellulose

8

glucose and galactose are absorbed into enterocytes how?

Na+ cotransport

9

fructose is absorbed how?

facilitated diffusion (GLUT 5)

10

glucose, galactose, and fructose are transferred from cell to blood how

facilitated diffusion (GLUT 2)

11

lactose intolerance is caused by a deficiency in?

lactase

12

lactose intolerance (what happens to lactose)

remains in GI as unabsorbed solute (decreasing water absorption of intestine and leading to diarrhea)
undigested lactose metabolized by colonic bacteria

13

symptoms of lactose intolerance

intestinal distension, borborygmi (gurgling noises in intestines), gas, diarrhea

14

sucrase-isomaltase deficiency is what kind of disorder and what happens

inherited
cannot digest sucrose and isomaltase

15

glucose/galactose malabsorption is caused by what?

genetic defect in glucose/galactose transporter (SGLT1)

16

what are the GI tacts two sources of proteins

endogenous- secretory proteins and cells shed into GI tract lumen
exogenous- dietary proteins

17

proteins are absorbed as what

amino acids, dipeptides, and tripeptides

18

essentially all ingested protein is what

assimilated

19

almost all glucose and galactose in intestine are what

absorbed

20

endopeptidases (what do they do and what types are there

hydrolyze interior peptide bonds
gastric pepsin
pancreatic enzymes

21

gastric pepsin (what does it do)

digests small amount of ingested protein

22

pancreatic enzymes are secreted as what

inactive precursors

23

trypsinogen is converted to trypsin by what?

enterokinase

24

enterokinase is secreted where

brush border in small intestine

25

trypsin autocatalysis the conversion of what

trypsinogen to trypsin
chymotrypsinogen to chymotrypsin
proeleastase to elastase
procarboxypeptidases A and B to carboxypeptidases A and B

26

exopeptidases (what do they do and name them)

hydrolyze one amino acid at a time fro C terminal end of proteins and peptides
carboxypeptisades A and B

27

carboxypeptidases A and B are secreted from where and converted by what

secreted from pancreas as proenzymes
converted to active enzymes by trypsin

28

what is the role of peptidases in brush border

cleave peptides produces by pancreatic proteases to oligopeptides and amino acids

29

how are most amino acids absorbed into enterocytes

Na+ cotransport

30

how are di and tripeptides absorbed into enterocytes (compared to amino acids and the transport mechanism)

faster and more efficiently than amino acids
H+ cotransport (PEPT1)

31

majority of proteins is absorbed as what

di and tri peptides (then hydrolyzed to amino acids as peptidases in enterocytes)

32

protein in stool is normally from what

bacteria and cellular debris

33

protein in stool is normally from what

bacteria and cellular debris

34

whole proteins can be absorbed but what is their significance

not nutritionally but immunological
can lead to food allergies

35

trypsin deficiency is cased by what

congenital lack of trypsin and pancreatic disease

36

cystinuria (what is it)

congenital defect that affects uptake of basic amino acids

37

Hartnup disease

congenital defect that affects uptake of neutral amino acids

38

familial iminoglycinuria

congenital defect that affects uptake of proline and hydroxyproline

39

what amount of iron ingested each day is absorbed

small fraction (about 10%)
amount absorbed about equal to amount lost

40

iron is absorbed in what forms

heme or free iron

41

what is the most easily absorbed form of iron

heme iron

42

who is heme iron absorbed

receptor mediated endocytosis or transporter protein (HCP1)

43

what form of free iron is more readily absorbed

Fe2+

44

gastric acid does what to iron which permits what

dissolves iron
allows it to form complex with ascorbic and citric acid (reduces ferric iron to ferrous)

45

Duodenal cytochrome B (Dcytb)
(what does it do)

reduces ferric to ferrous iron

46

how if ferrous iron transferred into enterocyte

ferrous iron transporter (DMT1)

47

in cell iron binds to what and forming what

apoferritin
forming ferritin for storage

48

iron is transported out of cell by what?

ferroportin

49

ferroportin and ferroxidase hephaestin doe what

convert ferrous to ferric iron

50

transferrin (where is it, what binds it, what does it do)

transferrin is in plasma and binds to ferric iron to transport it to other tissues

51

what mechanism is there for removing excess iron

no mechanism

52

most of iron regulation is orchestrated by what?

hepcidin

53

hepcidin (what does it regulate)

entry of iron into plasma by binding directly to ferroportin

54

binding fo hepcidin to ferroportin leads to what

internalization and degradation of ferroportin (blocks cellular iron export and recedes plasma iron)

55

when iron levels are low what are hepcidin levels like

low- leads to increase iron absorption and elevated iron release fro enterocytes

56

what is the most prevalent nutrient deficient

iron

57

most common cause of anemia in the world

iron deficiency

58

hemochromatosis (what is it)

chronic absorption of too much iron

59

most common genetic disorder in US

hereditary hemochromatosis

60

hemochromatosis (defect in)

HFE gene which causes hepcidin levels to drop

61

hemochromatosis (leads to)

excess iron collects in liver which can lead to cirrhosis and eventually liver cancer

62

hemochromatosis (issues other than with liver

damage pancreas- leading to diabetes
contribute to coronary disease

63

hemochromatosis (treatment)

periodically removing blood

64

electrolytes and water cross intestinal epithelial cells by what mechanisms

transcellular
paracellular

65

small intestines absorbs water and electrolytes from where

diet
salivary, gastric, biliary, and pancreatic secretions

66

failure of small intestines to absorb water and electrolytes leads to what

rapid dehydration, electrolyte imbalance and eventually circulatory collapse

67

failure of small intestines to absorb water and electrolytes leads to what

rapid dehydration, electrolyte imbalance and eventually circulatory collapse

68

Na is moved from lumen of small intestine across apical membranes of enterocytes how?

Na/glucose or Na/amino cotransport
Na/Cl cotransport
Na/H exchange

69

in duodenum and jejunum Na is absorbed by what mechanism(s)?

Na/glucose or Na/amino acid cotransport and Na/H exchange

70

in ileum Na is absorbed by what mechanism(s)?

Na/glucose or Na/amino acid cotransport and Na/H exchange
cotransport with Cl

71

in colon Na is absorbed by what mechanism(s)?

Na channels

72

Cl transport into enterocytes from lumen of intestine is mediated by what?

passive diffusion (paracellularly)
cotransport with Na and K
exchange with HCO3-

73

Cl transport into enterocytes is mediated by what?

passive diffusion (paracellularly)
cotransport with Na and K
exchange with HCO3-