Absorption and Export of Nutrients from the Small Intestine Enterocytes

[manohman]

---

Members do not see this ad.

Just want to clarify the absorption and export processes that go on in the small intestine.

Absorption wise...

Amino Acids = Always Active Transport
Carbohydrates = Secondary Active Transport (is this facilitated diffusion?)
Lipids = diffusion

Export =
Amino Acids = Active Transport?
Carbohydrates = Facilitated Diffusion (NOT Active Transport)
Lipids = Active via apoprotein Exocytosis

Bueno?

 

[sazerac]

Be careful... glucose and fructose are absorbed by different mechanisms in the intestinal cells, so you can't really simplify all carbohydrates like that.

The wikipedia Fructose page has a good diagram of how glucose requires a sodium co-transporter, while fructose just slides on in via the GLUT5 transporter.

 

[Thoroughbred_Med]

Just want to clarify the absorption and export processes that go on in the small intestine.

Absorption wise...

Amino Acids = Always Active Transport
Carbohydrates = Secondary Active Transport (is this facilitated diffusion?)
Lipids = diffusion

Export =
Amino Acids = Active Transport?
Carbohydrates = Facilitated Diffusion (NOT Active Transport)
Lipids = Active via apoprotein Exocytosis

Bueno?

No. This is not facilitated diffusion. It is exactly what you said it was, secondary active transport... meaning it is going from a region of low [glucose] to high [glucose] and needs to gather energy from a cotransporter to facilitate an otherwise energetically unfavorable process. For glucose, while getting absorbed in the brush border, it symports with a Na+ ion.

Now, when glucose arrives at the basolateral membrane of the small intestine cell there is a large [glucose]. To get from here to near by capillaries glucose molecules simply go via facilitated diffusion (NOT active transport)..... so you got it there.