Physiology of Carbohydrate and Protein Digestion and Absorption

Question 1

What type of digestion in the small intestine is mediated by pancreatic enzymes secreted into the duodenum?

Answer 1

Luminal

Question 2

What kind og digestion in the small intestine is mediated by enzymes situated at the brush border of epithelial cells?

Answer 2

Membrane

Question 3

Wat is the term for the overall process of digestion and absorption?

Answer 3

Assimilation

Question 4

Give an example of luminal hydrolysis of polymer to monomers?

Answer 4

Protein to amino acids

Question 5

Give and example of brushborder hydrolysis of oligomer to monomer?

Answer 5

Sucrose to glucose and fructose

Question 6

Give an example of intracellular hydrolysis?

Answer 6

Peptide

Question 7

Give an example of luminal hydrolysis followed by intracellular resynthesis?

Answer 7

Triacylglycerol to glycerol and fatty acids

Question 8

Name two polymers of glucose?

Answer 8

Starch and glycogen

Question 9

Name two oligosaccharides?

Answer 9

Sucrose and lactose

Question 10

What does glucose + fructose give?

Answer 10

Sucrose

Question 11

What does glucose + galactose give?

Answer 11

Lactose

Question 12

What is more highly branched - amylopectin or glycogen?

Answer 12

Glycogen

Question 13

What must all dietary carbohydrates be converted to for absorption?

Answer 13

Monosaccharides (glucose and fructose)

Question 14

What is the process of starch being broken down to oligosaccharides?

Answer 14

Intraluminal hydrolysis

Question 15

What are alpha-linit dextrins, maltotriose and maltose?

Answer 15

Oligosaccharides

Question 16

What is the process for breaking down oligosaccharides to monosaccharides?

Answer 16

Membrane digestion (at brush border)

Question 17

Name three oligosaccharidases?

Answer 17

Lactase
Maltase
Sucrase-isomaltase

Question 18

What accomplishes starch by intraluminakl hydrolysis to oligosaccharides?

Answer 18

Alpha-amylase (salivary and pacnreatic)

Question 19

What does a-amylase breakdown, and what does it not?

Answer 19

Breaks down linear internal alpha-1,4 linkages but not terminal alpha-1,4,linkages

Question 20

Does the endoenzyme a-amylase produce glucose?

Answer 20

No

Question 21

What enzyme, cannot cleave alpha-1,6 linkages at branch points (in amylopectin) ot alpha-1,4-linkages adjacent to branch points?

Answer 21

Alpha-amylase

Question 22

What are the main class of products from a-amylase?

Answer 22

Oligosaccharides

Question 23

What are integral membrane proteins with a catalytic domain that faces the lumen of the GI tract?

Answer 23

Oligosaccharidases

Question 24

Ohter than lactase, which breaks down lactose to glucose and galactose, what do all other oligosaccharidases cleave?

Answer 24

The terminal alpha-1,4-linkages of maltose, maltotriose and alpha-limit dextrins

Question 25

What oligosaccharidase is unique in that it is the only enzyme that can split the branching alpha-1,6,linkages of alpha-limit dextrins?

Answer 25

Isomaltase

Question 26

Give an example of a disorder caused by impaired carbohydrate digestion?

Answer 26

Lactose intolerance

Question 27

What insufficiency causes lactose intolerance?

Answer 27

Lactase deficiency

Question 28

What is primary lactase deficiency (primary hypolactasia) due to?

Answer 28

Lack of the lactase persistence (LP) allele

Question 29

What is secondary lactase deficiency due to?

Answer 29

Damage to/infection of/ the proximal small intestine

Question 30

Name a rare, autosomal recessive disease with no ability to digest lactose from birth?

Answer 30

Congenital lactase deficiency

Question 31

What are these produced in response to: short-chain fatty acids, hydrogen (can be detected in breath of lactase defiecient people), carbon dioxide and methane?

Answer 31

Produced by colonic microflora when lactose delivered to colon from ileum

Question 32

What are three symptoms of lactase insufficiency?

Answer 32

Bloating Abdominal Pain Flatulence

Question 33

What causes acidification of the colon and increased osmotic load - loose stools nad diarrhoea?

Answer 33

Undigested lactose

Question 34

What are the three final products of carbohydrate digestion?

Answer 34

Glucose, galactose and fructose

Question 35

Where does final product absorption occur?

Answer 35

In duodenum and jejunum

Question 36

What is absorbed by secondary active transport mediated by SGLT1?

Answer 36

Glucose and galactose

Question 37

What is absorbed by facilitated diffusion mediated by GLUT5?

Answer 37

Glucose and galactose

Question 38

How is exit for all monosaccharides mediated?

Answer 38

By facilitated diffusion by GLUT2

Question 39

For SGLT1 transport, what must the substrate be like?

Answer 39

A hexose in D conformation | Can form pyranose ring

Question 40

What products do endopeptidases produce?

Answer 40

Oligopeptides (2-6 amino acids)

Question 41

What products do exopeptidases produce?

Answer 41

Single amino acids