I will draw pictures, here. The luminal and contraluminal membranes have very different functions. One must take up nutrients from the intestine, one must deliver them to the blood. There is a problem - there is usually much more glucose within the epithelial cell than in the lumen of the intestine. Glucose, therefore, will have to travel 'up' a gradient.
Active transport is needed.
A transmembrane protein Sodium-Glucose transporter is present in the luminal side. This is a form of active transport . Once in the cell, the glucose then needs to get to the capillaries on the other side. This is a form of facilitated transport . The Golgi modifies proteins made in the RER and then helps to sort and send them to the proper place in the cell.