The rbc have, in fact, swollen to the extent that proteins leak out into the water. These red cell ghosts have been used to examine the biochemistry of membranes. They consist, fundamentally, of the phospholipid bilayer and associated proteins. These differences appear to be a feature of most eukaryotic cells. Proteins have also been analysed.
Epithelial cells line the intestine.
They are columnar in shape and are polarized cells - i.e. they are asymmetrical in structure and function. The lumenal and contralumenal membranes have very different functions. One must take up nutrients from the intestine, one must deliver them to the blood. A transmembrane protein Sodium-Glucose transporter is present in the luminal side. ATP 'drives' the formation of a potent electrochemical gradient across the cell membrane.