So, let's suppose our digestive enzymes found on the brush border break down the small peptides into tripepptides, dipeptides and amino acids. Let's begin by focusing on only the amino acids. So before the amino acids actually travel into the cytoplasm of our cells. So this is the cytoplasm side, this is the lumen side, so the apical side, and this other side is the basil lateral side. It basically is in close proximity to our blood vessels. So before these amino acids enter our cytoplasm, we have to establish an electrochemical gradient for sodium ions.