Eventually, the concentration of sodium outside is greater than inside of the cell. At this point, the sodium on the outside begins to travel into the cell via this cotransporter membrane protein. At the same time that the sodium travels, it basically brings those amino acids with it into our cytoplasm. Now, what about the tripepptides and dipeptides? So, at the same time that this pump basically brings the sodium on the outside, this basically brings the sodium back inside. So for every three sodium we bring outside, there's a sodium on the apical side that is brought inside.