Gastrointestinal Lecture 4 Part 2 Digestion and Absorption of dietary carbs

Question 1

What cleaves polysaccharides?

Answer 1

Question 2

What cleaves the disaccharides?

Answer 2

Question 3

The products of carbohydrate digestion

Answer 3

The products of carbohydrate digestion are monosaccharides that must cross the intestinal epithelium to be absorbed into the body

Question 4

Absorption of glucose/galactose

Answer 4

• Absorption of glucose/galactose is facilitated by secondary active transport
• SLGT-1 transports one molecule of glucose/galactose into intestine epithelial cell for every two Na+ ions that go in
• leaves via diffusion through GLUT2
• Na/K ATPase pump to replace Na+

Question 5

Absorption of fructose

Answer 5

Absorption of fructose occurs by facilitated diffusion

Question 6

Absorption of monosaccharides after a low sugar meal

Answer 6

normal

Question 7

Absorption of monosaccharides after a high sugar meal

Answer 7

gets overwhelmed/ saturated

Question 8

Summary of carbohydrate digestion and absorption

Answer 8

Question 9

examples of dietary fibre

Answer 9

> cellulose (plant cell walls)
> Lignin (plant cell walls; woody)
> chitin (cell walls of fungi [mushrooms] & insect/crustacean exoskeletons)

Question 10

physioloigcal effects of fibre

Answer 10

1. Delayed gastric emptying and increased satiety
2. Impaired absorption in the small intestine
   > multiple mechanisms: trapping, interfering, inhibiting

> Protective:

• delayed absorption of carbohydrates (better glucose control)
• Impaired cholesterol absorption
• Trapping of trace elements and possible toxic compounds

3. Fiber fermentation in the large intestine
> gut microbiota can ferment undigested fiber to produce short-chain fatty acids

4. Fecal bulking
> undigested fiber (mass and retained water), and increased bacterial mass secondary to fiber fermentation