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4.6: Protein Uptake, Absorption, Transport and Liver Uptake

Kansas State University: Human Nutrition · LibreTexts

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    From LibreTexts, under CC BY-NC-SA 4.0, as the source states it; its equations are written in TeX, which the PDF shows typeset. This page at LibreTexts.

    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).

    Diagram illustrating amino acid and peptide transporters in enterocytes, highlighting PepT1 and capillary absorption.
    Figure \(\PageIndex{1}\): Protein uptake and absorption

    The capillary inside a villus is shown below.

    Diagram of a blood vessel with labeled components: thin surface layer, capillaries, lacteal, and blood vessel structure.
    Figure \(\PageIndex{2}\): Anatomy of a villus1

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

    Illustration of the human digestive system highlighting the portal vein and small intestine with labeled arrows.
    Figure \(\PageIndex{3}\): 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.

    Diagram illustrating amino acid transport from circulation to hepatocytes, with pathways for protein synthesis, anabolic, and catabolic processes.
    Figure \(\PageIndex{4}\): Hepatic amino acid uptake
    ADAPT \(\PageIndex{1}\)

    References

    1. en.Wikipedia.org/wiki/File:In...simplified.svg
    2. commons.wikimedia.org/wiki/File:Gray591.png

    This page titled 4.6: Protein Uptake, Absorption, Transport and Liver Uptake was last modified on Thu, 29 Jan 2026 17:43:04 GMT and is shared under a CC BY-NC-SA 4.0 license and was authored, remixed, and/or curated by Brian Lindshield via source content that was edited to the style and standards of the LibreTexts platform.