Protein Digestion

Front 1

1. In what form is nitrogen shuttled back and forth between tissues?

Back 1

a. Amino acids

Front 2

2. Where does protein digestion begin? Where is it completed?

Back 2

a. In the stomach
b. Completed in the small intestine

Front 3

3. What parts of the digestive tract secrete proteolytic enzymes?

Back 3

b. Pancreas
c. Intestinal mucosa

Front 4

4. What cells are responsible for the production of acid?

Back 4

a. Parietal cells of gastric mucosa

Front 5

5. What do parietal cells secrete?

Back 5

a. HCl
b. KCl

Front 6

6. How is acid produced in parietal cells?

Back 6

a. H+ is pumped into lumen of parietal cell by K/K+ ATPase
b. Cl- is exchanged for HCO3 in membrane facing interstitial fluid
c. Cl- is actively pumped into lumen of parietal cell

Front 7

7. What are the functions of gastric acid in protein digestion?

Back 7

a. Initiation of conversion of pepsinogen to pepsin
b. Contributes to denaturation of proteins

Front 8

8. What stimulates acid secretion?

Back 8

a. Gastrin
b. Acetylcholine

Front 9

9. What stimulates gastrin release?

Back 9

a. Stimulation of stretch receptors in stomach wall
b. Respond to physical activator of acid secretion by parietal cells

Front 10

10. What is an ulcer?

Back 10

a. Erosion of the GI lining

Front 11

11. How does aspirin make an ulcer worse?

Back 11

a. Aspirin decreases prostaglandins, which help maintain integrity of stomach lining
b. Less stomach lining leads to higher susceptibility to ulcers

Front 12

12. How do new anti-ulcer drugs work?

Back 12

a. Block acid secretion

Front 13

a. What is the major protease in gastric juice?

Back 13

i. Pepsin

Front 14

c. What type of cell secretes pepsinogen?

Back 14

i. Chief cells

Front 15

a. How many amino acids are removed in the pepsin→ pepsinogen conversion?

Back 15

i. 42

Front 16

b. What type of peptide bonds does pepsin hydrolyze?

Back 16

i. Peptide bonds in which the carboxyl group is contributed by an aromatic amino acid

Front 17

c. What type of amino acids have a carboxyl group contributed by an aromatic amino acid?

Back 17

i. Phenylalanine
ii. Tyrosine
iii. Tryptophan

Front 18

d. What causes pepsinogen secretion?

Back 18

i. Acetylcholine
ii. Neural reflex triggered by presence of acid in stomach

Front 19

a. What is the pH of pancreatic juices?

Back 19

i. Alkaline

Front 20

b. What zymogens does the pancreas secrete?

Back 20

i. Trypsin
ii. Chymotrypsin
iii. Elastase
iv. Carboxypeptidases A and B

Front 21

d. What enzyme converts trypsinogen to trypsin? What secretes this enzyme?

Back 21

i. Enteropeptidase
ii. Intestinal mucosal cells

Front 22

e. What role does trypsin play in digestion?

Back 22

i. Activation of remaining pancreatic zymogens to active proteolytic enzymes

Front 23

f. What does trypsin hydrolyze?

Back 23

i. Arginine
ii. Lysine

Front 24

h. What does chymotrypsin hydrolyze?

Back 24

i. Aromatic amino acids

Front 25

i. What does carboxypeptidases A cleave?

Back 25

i. Aliphatic AA residues from carboxy terminal

Front 26

j. What does carboxypeptidase B cleave?

Back 26

i. Arginine
ii. Lysine

Front 27

k. What is the zymogen of elastase?

Back 27

i. Proelastase

Front 28

l. What does elastase cleave?

Back 28

i. Neutral aliphatic amino acids

Front 29

m. What hormones work in concert to stimulate pancreatic secretions?

Back 29

i. Secretin
ii. Cholecystokinin (CCK)

Front 30

n. What secretes secretin? What stimulates its release?

Back 30

i. Endocrine cells in the duodenum
ii. Decrease in pH as acidic mixture enters duodenum from stomach

Front 31

o. What secretes cholecystokinin? What stimulates its release?

Back 31

i. Endocrine cells throughout the small intestine
ii. Presence of fat and protein in small intestine

Front 32

p. What does cholecystokinin stimulate?

Back 32

i. Synthesis and secretion of pancreatic proteolytic enzymes

Front 33

a. What is the function of aminopeptidase and dipeptidase?

Back 33

i. Hydrolysis of these small peptides to amino acids after their entry into mucosal cells

Front 34

b. What is the specific function of an aminopeptidase?

Back 34

i. Successively remove amino acids from amino terminus of a polypeptide

Front 35

a. Where does amino acid absorption occur?

Back 35

i. Small intestine

Front 36

b. How would you describe transport of amino acids into intestinal mucosal cells?

Back 36

i. Active process
ii. Dependent on co-transport with Na+ → Na symport

Front 37

c. What does the ASC system transport?

Back 37

i. Neutral amino acids
ii. Serine, alanine, and cysteine

Front 38

d. What does the A system transport?

Back 38

i. Neutral amino acids
ii. Glycine and alanine

Front 39

e. What does the L system transport?

Back 39

i. Neutral amino acids
ii. Branched chain and phenylalanine

Front 40

f. What does the Gly system transport?

Back 40

i. Glycine
ii. Proline
iii. Hydroxyproline

Front 41

g. What does the N system transport?

Back 41

i. Histidine
ii. Asparagine
iii. Glutamine

Front 42

h. What does the anionic system transport?

Back 42

i. Glutamate
ii. Aspartate

Front 43

i. What does the cationic system transport?

Back 43

i. Base amino acids
ii. Cysteine

Front 44

j. What amino acid transport systems are not dependent on Na/K pump?

Back 44

i. L
ii. Cationic

Front 45

k. What does deficiency in cationic transporter lead to?

Back 45

i. Cystinuria
ii. Stone formation due to insolubitlity of high cystine concentration

Front 46

l. How do you treat cystinuria? How does it work?

Back 46

i. Penicillamine
ii. Forms mixed disulfides with cysteine to lower cystine concentration

Front 47

m. What causes Hartnup’s disease? What are the symptoms?

Back 47

i. Deficiency in transport system A
ii. Neurological symptoms
iii. Pellagra→ due to lack of niacin

Front 48

n. What causes Joseph’s syndrome? What does it lead to?

Back 48

i. Deficiency in Gly transport system
ii. Iminoglycinuria

Front 49

o. What leads to lysinuric protein intolerance?

Back 49

i. Results from a defect in cationic transport