3.b Intestinal phases Flashcards
Hydrolysis of starch by amylase: what will you end up with?
glucose, maltose, isomaltose
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
- Intestinal lumen
- Na+
- Glucose
- Galactose
- Na+
Which monomer has a different absorption? What type does it use?
Fructose has a different absorption: it uses passive diffusion. There are all different kinds of transporters per enterocyte, all maximizing the absorption of monomers.
Starch digestion is performed by two major dual enzymes: sucrase-isomaltase and maltase-glucoamylase. What is their activity?
Sucrase-isomaltase: both cleaves sucrose into monomers and maltose/maltotrioses/dextrins into glucose.
Maltase-glucoamylase: also cleaves maltotrioses/maltose into glucose.
Presence of dextrins inhibit/increase activity of maltase-glucoamylase
inhibit
Meal glucose is completely/almost completely/ not completely absorbed along the human small intestine
completely
What is the mean carbohydrate absorption from food?
98%
Where does the glucose get absorbed mostly in the small intestine?
Much individual variation
What are the three sites of protein digestion?
Three sites of protein digestion
1. Inside lumen
2. Brush border
3. Cleavage Inside enterocyte (this you do not have for carbohydrates)
Can amino acids be freely absorbed into the enterocytes?
No, they have specific transporters. Just as with dipeptides and tripeptides.
What atoms are needed for import of amino-acids?
Sodium. This so-called ‘co-transporter’ is ALWAYS needed. Amino acids = ACTIVE transport.
What is the mean protein absorption from food?
93%. Less individual variation than carbohydrates.
Removal of dietary protein by digestion and absorption occurs throughout..
Small intestine
Bile acids are synthesized from..
Cholesterol
In what form are fat-soluble vitamins, carotenes and other lipids absorbed?
Luminal lipid micelles, they have a hydrophilic outside and a hydrophobic inside
How is absorption of fat performed?
Bile salts > lipase from pancreas > digesting triglycerides into monoglyceride <> micelles, fatty acids can now be absorbed
What happens after absorption?
After absorption: fatty acids are used to synthesize again triglycerides. Are captured by proteins, those form chylomicrons
What are chylomicrons?
= spheres that contain triglyceride, synthesized in the enterocytes and released into the body. NOT in the bloodstream, but in the lacteal (lymphatic system).
To what organ do lipids go after absorption?
Lipids pass around the liver and go straight to the heart. Heart relies mostly on fat metabolism.
Absorption rate of fat?
Absorption: increased compared to protein, decreased compared to carbohydrates. 95%.
In what part of the small intestine is fat mostly absorbed?
Jejenum
What happens if lipids are not absorbed and they come to the end of the ileum?
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
Name the regions of the colon in order of the food particle
Cecum > ascending colon > transverse colon > descending colon > rectum > anal sphincter
The ileocecal valve is..
portal between ileum and cecum
Large intestine has more/less movements than small intestine
Way more
A meal of 12-36hr will be equally mixed. This means that defecation..
does not depend on the hrs of intake.
Colonic response to a meal is initiated by..
signals from the stomach and intestine
What does ano-rectal distension (uitzetten) do?
Initiates a defecation response. Surrounding muscles are noticed. There is an involuntary and voluntary defecation reflex.
Arterial splanchnic bloodflow = ?
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.
What organ absorbs almost all of your water intake?
Large water flow into the intestines, for digestion and absorption of nutrients. GI tract absorbs almost all of the water.
