Protein digestion & absorption: digestion begins in the stomach through the actions of pepsin, which is converted from pepsinogen by the release of acid, which is in turn stimulated by ach. Pepsin takes care of 15% of the proteolysis, and the rest takes place due to pancreatic proteases. Unlike carbohydrates, you can absorb proteins in the form of individual amino acids, di- or tri-peptides. For individual amino acids, there is an apical transporter that is identical to the na/amino acid transporter just like the na/glucose transporter except the stoiciometric relationship is 1:1 instead of 2:1. On the basolateral surface, na is removed by the na. Atpase, and the amino acids are moved out via channels or a facilitated diffusion carrier. The four carriers respond to different types of amino acids (acidic, basic, neutral, imino acids); these carriers are less specific because 4-7 acids can bind to any carriers.