There are a number of similarities between carbohydrate and protein uptake, absorption, transport, and uptake by the liver. Hopefully after this section you will understand these similarities.

Over 60% of all amino acids are taken up into the enterocyte as di- and tripeptides through the PepT1 transporter. Individual amino acids are taken up through a variety of amino acid transporters. Once inside the enterocyte, peptidases cleave the peptides to individual amino acids. These cleaved amino acids, along with those that were taken up as individual amino acids, are moved into the capillary by another variety of amino acid transporters (some are the same as on the brush border, some are different).

Figure 4.61 Protein uptake and absorption

The capillary inside a villus is shown below.

Figure 4.62 Anatomy of a villus¹

Like monosaccharides, amino acids are transported directly to the liver through the portal vein.

Figure 4.63 The portal vein transports monosaccharides and amino acids to the liver²

Amino acids are taken up into the hepatocyte through a variety of amino acid transporters. The amino acids can then be used to either make proteins or are broken down to produce glucose, as will be described in chapter 6.

Figure 4.64 Hepatic amino acid uptake

References & Links

1. http://en.wikipedia.org/wiki/File:Intestinal_villus_simplified.svg

2. https://commons.wikimedia.org/wiki/File:Gray591.png

Videos

Absorption in the Small Intestine – http://www.youtube.com/watch?v=P1sDOJM65Bc