Mechanism for Nutrient Transport

Dan Marquez dmarquez3 at socal.rr.com
Fri Mar 21 15:12:57 EST 2003


Mikael,

Thank you for the informative post! It is appreciated!

You wrote...

> The endproduct of the digestion is
> Hexoses, pentoses (simple sugars), amino acids, di and tripeptides,
> and free fatty acids.

That is good info.

> The next step is called absorption and is the process by witch the
> nutrient is taken from the intestine to the bloodstream (sugars,
> aminoacids and free fatty acids whit less than 10-12 carbon atoms) or
> the lymph other fatty acids.

This answers the riddle if the nutrients go into the lymph or the blood...
the answer is BOTH.

> The carbohydrates is taken into the cells lining the intestine by
> three different mechanisms.
>1. Glucose and galactose is cotransported...
> 2. Fructose is taken in by transporters...
> 3. Pentoses is taken in by simple diffusion.
> From the cells to the bloodstream the sugars
> uses another transporter, Glut 2.

Where do these transporters reside, and where do they come from?  Do people
ever get disease from transporter shortages?

> Aminoacids and peptides i stransported in a simmiliar way as the
> sugars.

I guess this will become clear with the answer to the last question. I am
wondering if a unpaired transporter is a biomolecule that drifts in the
blood or lymph, outside any cell.

> The free fatty acids is taken in to the cells by diffusion and when
> they are inside the cells the ones containing more than 10-12 carbons
> are esterified into triglycerides and coated whit a layer of protein,
> cholesterol and phospholipids to form what is known as chylomicrons
> and enter the lympha.

Does this mean the cells, whichever ones they are, secrete chylomicrons into
the lymph, and not into the bloodstream?


> When this thing is bound the transporter
> change its configuration so that the bound substans is transported
> trough the membrane.

Hmm... I guess you mean into the cell, right?

>... the pool of Glut 4 move to the
> cells membrane.

Let's see if I understand this.  Free-floating glucose somehow penetrates
from the intestines to the blood without a transporter. It floats in the
bloodstream until it bumps into a cell that has Glut 4 expressed. Then the
Glut 4 sucks up the glucose. If we cave sugar, that is because a lot of
cells are expressing Glut 4. Right?

> The answer to why the immunsysten doesn't think that a nutrient is a
> antigen is becouse it is broken down into free fatty acids, amino
> acids and simple sugars.

That is quite true.  I was trying to understand a mechanism that might allow
larger nutrients to enter the lymph or bloodstream, triggering Crohn's
Disease where the nutrients are attacked.

Thanks!

Dan





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