Figure 4.

Potential pathways of amino acid and peptide absorption in the small intestine. (1) paracellular through widened tight junctions, (2) passive diffusion through the enterocyte, (3) endocytosis, followed by carrier transport or suggested peptide cargo*-permeability, (4) Transport carrier mediated passage *It is unlikely that peptides will passively diffuse across the cell membrane, but altering their physical properties (such as conformational flexibility and polarity), has been proposed to improve their permeability, also referred to as peptide cargo (243). Open dots represent amino acids, open dot-chains represent digestible peptides, closed dot-chains represent proteolysis resistant gluten peptides. Modified from Brouns and Shewry (202).