Lecture 19 - Digestion and Absorption of Protein

Question 1

_________ are enzymes that need to be cleaved at one or more sites in order to become active/functioning.

A. Proenzymes
B. Endopeptidases
C. Exopeptidases

Answer 1

A

Question 2

__________ cleave proteins by hydrolyzing peptide bonds within the polypeptide chain.

A. Proenzymes
B. Endopeptidases
C. Exopeptidases

Answer 2

B

Question 3

_________ cleave AA from either N or C terminal ends of peptides or proteins.

Answer 3

C

Question 4

Pepsin is produced by what organ?

Answer 4

stomach

Question 5

Trypsin and chymotrypsin are produced by what organ?

Answer 5

pancreas

Question 6

Peptidases are produced by what organ?

Answer 6

small intestine

Question 7

What are two non-enzymatic components of gastric juice?

Answer 7

1. Gastin

2. HCl

Question 8

Gastrin acts on the _______ cells to secrete HCl.

Answer 8

parietal

Question 9

Gastrin acts on the ________ cells to secrete pepsinogen.

Answer 9

chief

Question 10

HCl decreases pH to denature protein and provide a proper environment for _______.

Answer 10

pepsin

Question 11

Secretin and CCK are secreted in response to what?

Answer 11

Chyme moving through duodenum

Question 12

Secretin stimulates the release of _________.

Answer 12

pancreatic juice

Question 13

CCK stimulates the release of ___________ into the lumen of the small intestine.

Answer 13

pancreatic zymogens

Question 14

Enteropeptidase catalyzes what reaction?

Answer 14

Conversion of trypsinogen to trypsin

Question 15

What are the (2) products of protein digestion within the lumen of the small intestine?

Answer 15

35% neutral and basic AA

65% oligopeptides

Question 16

In the pathway of AA transport from the lumen of the SI to the portal blood, AA first go through the brush border where they are further hydrolyzed by _____.

Answer 16

oligopeptidases

Question 17

Dipeptides and tripeptides are taken up by AA transporters using a _________ and then hydrolyzed by peptidases in intestinal cells.

Answer 17

proton gradient

Question 18

Transport proteins (most are Na+ dependent) take AA through the _______ membrane, from the intestinal cell to the portal blood.

Answer 18

basolateral

Question 19

Enteropeptidases are found where?

Answer 19

Brush border of intestinal cells

Question 20

If an AA can’t be absorbed in the intestine, it also can’t be absorbed in the ________ and is excreted.

Answer 20

kidney

Question 21

Long-term use of proton pump inhibitors can result in _________________.

Answer 21

vitamin B12 deficiency

Question 22

What are two enzymes that require B12 as a cofactor?

Answer 22

1. Methylmalonyl-CoA mutase (synthesizes succinyl-CoA in TCA cycle)
2. Methionine synthase

Question 23

Succinyl-CoA is required for _________ synthesis, so a B12 deficiency results in megaloblastic anemia.

Answer 23

heme