3.b Intestinal phases

Question 1

Hydrolysis of starch by amylase: what will you end up with?

Answer 1

glucose, maltose, isomaltose

Question 2

Starch is digested in the 1
2 is pumped from the mucosal cell into lumen
3 and 4 and 5 pumped back into the mucosal cell with a transporter

Answer 2

1. Intestinal lumen
2. Na+
3. Glucose
4. Galactose
5. Na+

Question 3

Which monomer has a different absorption? What type does it use?

Answer 3

Fructose has a different absorption: it uses passive diffusion. There are all different kinds of transporters per enterocyte, all maximizing the absorption of monomers.

Question 4

Starch digestion is performed by two major dual enzymes: sucrase-isomaltase and maltase-glucoamylase. What is their activity?

Answer 4

Sucrase-isomaltase: both cleaves sucrose into monomers and maltose/maltotrioses/dextrins into glucose.

Maltase-glucoamylase: also cleaves maltotrioses/maltose into glucose.

Question 5

Presence of dextrins inhibit/increase activity of maltase-glucoamylase

Answer 5

inhibit

Question 6

Meal glucose is completely/almost completely/ not completely absorbed along the human small intestine

Answer 6

completely

Question 7

What is the mean carbohydrate absorption from food?

Answer 7

98%

Question 8

Where does the glucose get absorbed mostly in the small intestine?

Answer 8

Much individual variation

Question 9

What are the three sites of protein digestion?

Answer 9

Three sites of protein digestion
1. Inside lumen
2. Brush border
3. Cleavage Inside enterocyte (this you do not have for carbohydrates)

Question 10

Can amino acids be freely absorbed into the enterocytes?

Answer 10

No, they have specific transporters. Just as with dipeptides and tripeptides.

Question 11

What atoms are needed for import of amino-acids?

Answer 11

Sodium. This so-called ‘co-transporter’ is ALWAYS needed. Amino acids = ACTIVE transport.

Question 12

What is the mean protein absorption from food?

Answer 12

93%. Less individual variation than carbohydrates.

Question 13

Removal of dietary protein by digestion and absorption occurs throughout..

Answer 13

Small intestine

Question 14

Bile acids are synthesized from..

Answer 14

Cholesterol

Question 15

In what form are fat-soluble vitamins, carotenes and other lipids absorbed?

Answer 15

Luminal lipid micelles, they have a hydrophilic outside and a hydrophobic inside

Question 16

How is absorption of fat performed?

Answer 16

Bile salts > lipase from pancreas > digesting triglycerides into monoglyceride <> micelles, fatty acids can now be absorbed

Question 17

What happens after absorption?

Answer 17

After absorption: fatty acids are used to synthesize again triglycerides. Are captured by proteins, those form chylomicrons

Question 18

What are chylomicrons?

Answer 18

= spheres that contain triglyceride, synthesized in the enterocytes and released into the body. NOT in the bloodstream, but in the lacteal (lymphatic system).

Question 19

To what organ do lipids go after absorption?

Answer 19

Lipids pass around the liver and go straight to the heart. Heart relies mostly on fat metabolism.

Question 20

Absorption rate of fat?

Answer 20

Absorption: increased compared to protein, decreased compared to carbohydrates. 95%.

Question 21

In what part of the small intestine is fat mostly absorbed?

Answer 21

Jejenum

Question 22

What happens if lipids are not absorbed and they come to the end of the ileum?

Answer 22

Fat in ileum and colon: PYY (hormone peptide YY) release. > inhibition of meal-stimulated GI functions. Slowing everything down, to enhance absorption of the lipids

Question 23

Name the regions of the colon in order of the food particle

Answer 23

Cecum > ascending colon > transverse colon > descending colon > rectum > anal sphincter

Question 24

The ileocecal valve is..

Answer 24

portal between ileum and cecum

Question 25

Large intestine has more/less movements than small intestine

Answer 25

Way more

Question 26

A meal of 12-36hr will be equally mixed. This means that defecation..

Answer 26

does not depend on the hrs of intake.

Question 27

Colonic response to a meal is initiated by..

Answer 27

signals from the stomach and intestine

Question 28

What does ano-rectal distension (uitzetten) do?

Answer 28

Initiates a defecation response. Surrounding muscles are noticed. There is an involuntary and voluntary defecation reflex.

Question 29

Arterial splanchnic bloodflow = ?

Answer 29

The splanchnic circulation supplies the alimentary tract.
Aorta > organs of small intestines, stomach, pancreas, colon and liver.
Flow from these organs is all via the portal vein, through the liver to protect the body from an overflow of nutrients.

Question 30

What organ absorbs almost all of your water intake?

Answer 30

Large water flow into the intestines, for digestion and absorption of nutrients. GI tract absorbs almost all of the water.