9. Digestion and Absorption of Protein and Carbohydrates

Question 1

Where are the principle sites for protein digestion?

Answer 1

Stomach

Small intestine

Question 2

What digestion of protein occurs in the mouth?

Answer 2

Chewing

Saliva aids swallowing

Question 3

What type of cells release pepsinogen in the stomach?

Answer 3

Chief cells

Question 4

What type of an enzyme is pepsin?

Answer 4

Endopeptidase

Question 5

What converts pepsinogen to pepsin?

Answer 5

HCl

Question 6

What are the two major pancreatic enzymes in protein digestion?

Answer 6

Chymotrypsin

Trypsin

Question 7

What converts trypsinogen to trypsin?

Answer 7

Enteropeptidase

Question 8

What converts chymotrypsinogen, proelastase and procarboxypeptidase to their active forms?

Answer 8

Trypsin

Question 9

What types of enzymes are trypsin, chymotrypsin and elastase?

Answer 9

Endo-peptidase

MOA: Serine protease

Question 10

What types of enzymes are carboxypeptidase A and B?

Answer 10

Carboxypeptidases

MOA: Metalloprotease (Zn++)

Question 11

What types of bonds does trypsin cleave?

Answer 11

Adjacent to basic AAs

Question 12

What types of bonds does chymotrypsin cleave?

Answer 12

Adjacent to hydrophobic AAs

Question 13

What types of bonds does elastase cleave?

Answer 13

Adjacent to small AAs

Question 14

What types of bonds does Carboxypeptidase A cleave?

Answer 14

Hydrophobic AAs at C-terminus

Question 15

What types of bonds does Carboxypeptidase B cleave?

Answer 15

Basic AAs at C-terminus

Question 16

What are the products of protein digestion?

Answer 16

Tetra-peptides
Tri-peptides
Amino acids

Question 17

What are the principle sites of carbohydrate digestion?

Answer 17

Mouth

Intestinal lumen

Question 18

What carbohydrate digestion occurs in the mouth?

Answer 18

Chewing

Salivary amylase hydrolyses random a(1>4) bonds

Question 19

What pancreatic enzymes are involved in carbohydrate metabolism?

Answer 19

Endoglycosidases
Disaccharidases
Oligosaccharidases

Question 20

What enzymes are used to breakdown maltose and maltotriose?

Answer 20

Glucoamylase, sucrase, maltase

Question 21

What are the breakdown products of maltose, maltotriose and trehalose?

Answer 21

2 glucose

Question 22

What breaks down sucrose?

Answer 22

Sucrase

Question 23

What are the breakdown products of sucrose?

Answer 23

Glucose and fructose

Question 24

What breaks down lactose?

Answer 24

Lactase

Question 25

What are the breakdown products of lactose?

Answer 25

Glucose and galactose

Question 26

What breaks down trehalose?

Answer 26

Trehalase

Question 27

What is the cause of lactose intolerance?

Answer 27

Insufficient lactase

Undigested lactose builds up in the large intestine, and get digested by bacteria, which produce gases

Question 28

Which enzymes are anchored to the microvilli?

Answer 28

Aminopeptidase
Endopeptidase
Carboxypeptidase
Dipeptidase
Disaccharidases
Oligosaccharidases

Question 29

What form is protein absorbed most rapidly?

Answer 29

Peptides

Question 30

How are peptides absorbed into the enterocyte?

Answer 30

Coupled to a H+ gradient, which is maintained by a Na+/H+ exchanger
Metabolised into free AAs in the enterocyte, which can be absorbed into the blood

Question 31

How is protein released into the interstitial fluid?

Answer 31

Facilitated diffusion
Co-transport
Glutamate and aspartate are used as energy and not transported out of enterocyte

Question 32

Describe the transport of monosaccharides into and out of the enterocyte?

Answer 32

1. Glucose and Na+ bind to SGLT on luminal membrane
2. Na+ moves down electrochemical gradient
3. Na/K exchanger pumps Na+ out of the cell
4. GLUT transports glucose into interstitial fluid