Basic amino acids and cystine. Acidic amino acid transport system. The basic mechanism of amino acid transport is a sodium co-transport mechanism similar to that used for glucose. Dipeptide transport becomes very important in individuals who are deficient in a single amino acid transporter, since this allows uptake of the deficient amino acid as a dipeptide. However, most absorption occurs via the primary amino acid carriers normally.
Micelles diffuse to the epithelial cell surface and come into contact with the brush border.
The high lipid solubility of the digestion products allows them to quickly diffuse across the epithelial cell membrane. There also is some evidence for fatty acid specific transporters. Bile salts are not reabsorbed but recirculate within the chyme to ferry more lipid digestion products to the brush border. Inside the epithelial cell the fragments of lumenal lipid metabolism are resynthesized into triglycerides, phospholipids and cholesterol esters. This vesicular structure is referred to as a chylomicron .