Digestion and Absorption of Carbohydrates and Proteins

Question 1

carbohydrates must be what before being absorbed

Answer 1

digested into monosaccharides

Question 2

starches are converted by what into what

Answer 2

salivary and pancreatic alpha-amylases

to maltose, maltotriose, and alpha-limit dextrins

Question 3

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

Answer 3

glucoamylase, isomaltase, and maltase

brush border of membrane

Question 4

sucrose is cleaved by what into what?

Answer 4

sucrase

fructose and glucose

Question 5

lactose is cleaved by what into what

Answer 5

lactase

glucose and galactose

Question 6

trehalose is what (what cleaves it)

Answer 6

glucose dimer

trehalase

Question 7

what is not digested by human enzymes

Answer 7

cellulose

Question 8

glucose and galactose are absorbed into enterocytes how?

Answer 8

Na+ cotransport

Question 9

fructose is absorbed how?

Answer 9

facilitated diffusion (GLUT 5)

Question 10

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

Answer 10

facilitated diffusion (GLUT 2)

Question 11

lactose intolerance is caused by a deficiency in?

Answer 11

lactase

Question 12

lactose intolerance (what happens to lactose)

Answer 12

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

Question 13

symptoms of lactose intolerance

Answer 13

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

Question 14

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

Answer 14

inherited

cannot digest sucrose and isomaltase

Question 15

glucose/galactose malabsorption is caused by what?

Answer 15

genetic defect in glucose/galactose transporter (SGLT1)

Question 16

what are the GI tacts two sources of proteins

Answer 16

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

Question 17

proteins are absorbed as what

Answer 17

amino acids, dipeptides, and tripeptides

Question 18

essentially all ingested protein is what

Answer 18

assimilated

Question 19

almost all glucose and galactose in intestine are what

Answer 19

absorbed

Question 20

endopeptidases (what do they do and what types are there

Answer 20

hydrolyze interior peptide bonds
gastric pepsin
pancreatic enzymes

Question 21

gastric pepsin (what does it do)

Answer 21

digests small amount of ingested protein

Question 22

pancreatic enzymes are secreted as what

Answer 22

inactive precursors

Question 23

trypsinogen is converted to trypsin by what?

Answer 23

enterokinase

Question 24

enterokinase is secreted where

Answer 24

brush border in small intestine

Question 25

trypsin autocatalysis the conversion of what

Answer 25

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

Question 26

exopeptidases (what do they do and name them)

Answer 26

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

Question 27

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

Answer 27

secreted from pancreas as proenzymes | converted to active enzymes by trypsin

Question 28

what is the role of peptidases in brush border

Answer 28

cleave peptides produces by pancreatic proteases to oligopeptides and amino acids

Question 29

how are most amino acids absorbed into enterocytes

Answer 29

Na+ cotransport

Question 30

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

Answer 30

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

Question 31

majority of proteins is absorbed as what

Answer 31

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

Question 32

protein in stool is normally from what

Answer 32

bacteria and cellular debris

Question 33

protein in stool is normally from what

Answer 33

bacteria and cellular debris

Question 34

whole proteins can be absorbed but what is their significance

Answer 34

not nutritionally but immunological | can lead to food allergies

Question 35

trypsin deficiency is cased by what

Answer 35

congenital lack of trypsin and pancreatic disease

Question 36

cystinuria (what is it)

Answer 36

congenital defect that affects uptake of basic amino acids

Question 37

Hartnup disease

Answer 37

congenital defect that affects uptake of neutral amino acids

Question 38

familial iminoglycinuria

Answer 38

congenital defect that affects uptake of proline and hydroxyproline

Question 39

what amount of iron ingested each day is absorbed

Answer 39

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

Question 40

iron is absorbed in what forms

Answer 40

heme or free iron

Question 41

what is the most easily absorbed form of iron

Answer 41

heme iron

Question 42

who is heme iron absorbed

Answer 42

receptor mediated endocytosis or transporter protein (HCP1)

Question 43

what form of free iron is more readily absorbed

Answer 43

Fe2+

Question 44

gastric acid does what to iron which permits what

Answer 44

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

Question 45

Duodenal cytochrome B (Dcytb) | what does it do

Answer 45

reduces ferric to ferrous iron

Question 46

how if ferrous iron transferred into enterocyte

Answer 46

ferrous iron transporter (DMT1)

Question 47

in cell iron binds to what and forming what

Answer 47

apoferritin | forming ferritin for storage

Question 48

iron is transported out of cell by what?

Answer 48

ferroportin

Question 49

ferroportin and ferroxidase hephaestin doe what

Answer 49

convert ferrous to ferric iron

Question 50

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

Answer 50

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

Question 51

what mechanism is there for removing excess iron

Answer 51

no mechanism

Question 52

most of iron regulation is orchestrated by what?

Answer 52

hepcidin

Question 53

hepcidin (what does it regulate)

Answer 53

entry of iron into plasma by binding directly to ferroportin

Question 54

binding fo hepcidin to ferroportin leads to what

Answer 54

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

Question 55

when iron levels are low what are hepcidin levels like

Answer 55

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

Question 56

what is the most prevalent nutrient deficient

Answer 56

iron

Question 57

most common cause of anemia in the world

Answer 57

iron deficiency

Question 58

hemochromatosis (what is it)

Answer 58

chronic absorption of too much iron

Question 59

most common genetic disorder in US

Answer 59

hereditary hemochromatosis

Question 60

hemochromatosis (defect in)

Answer 60

HFE gene which causes hepcidin levels to drop

Question 61

hemochromatosis (leads to)

Answer 61

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

Question 62

hemochromatosis (issues other than with liver

Answer 62

damage pancreas- leading to diabetes | contribute to coronary disease

Question 63

hemochromatosis (treatment)

Answer 63

periodically removing blood

Question 64

electrolytes and water cross intestinal epithelial cells by what mechanisms

Answer 64

transcellular | paracellular

Question 65

small intestines absorbs water and electrolytes from where

Answer 65

diet | salivary, gastric, biliary, and pancreatic secretions

Question 66

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

Answer 66

rapid dehydration, electrolyte imbalance and eventually circulatory collapse

Question 67

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

Answer 67

rapid dehydration, electrolyte imbalance and eventually circulatory collapse

Question 68

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

Answer 68

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

Question 69

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

Answer 69

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

Question 70

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

Answer 70

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

Question 71

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

Answer 71

Na channels

Question 72

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

Answer 72

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

Question 73

Cl transport into enterocytes is mediated by what?

Answer 73

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