These studies are aimed at examining the structural and functional properties of the intestinal cell as they relate to absorption. Since substances absorbed by the intestine must traverse the outer (luminal) microvillus membrane, the chemical and enzymatic properties of this surface are undoubtedly important in the absorptive process. We have recently isolated the lateral and basal plasma membranes and therefore we will be comparing the structural and functional similarities and differences of these two cell components. Our objectives are threefold: (1) to further characterize and isolate in purer form the intestinal plasma membranes and to relate these to transport; (2) to study the nature of the glycolipids and glycoproteins of intestinal cell plasma membranes and to examine their possible role in the transport of carbohydrates, amino acids and lipids; and (3) to extend our previous findings on the mucosal uptake of macromolecules in order to determine the mechanism and to examine the effect of agents such as polybasic and polyacidic amino acids on this process.