Final answer:
The apical membrane is specialized for absorption and secretion, containing symporters and channels, while the basolateral membrane has pumps like the Na+/K+ ATPase. They are separated by tight junctions that maintain the cell's polarity. The cell membrane is a phospholipid bilayer with embedded proteins specific to each region's function.
Step-by-step explanation:
The apical and basolateral regions of the cell membrane differ in their structure, function, and the types of transport proteins they contain. The apical membrane faces the lumen or open space of a cavity or tube and is specialized for the absorption and secretion of molecules. For instance, it contains Na+/Cl- symporters for the reabsorption of ions. It also features leaky channels allowing substances like K+ to move back into the lumen. In contrast, the basolateral membrane, facing the connective tissue base and adjacent to the basement membrane, contains pumps like the Na+/K+ ATPase which create an electrochemical gradient essential for the function of the apical symporters.
The two regions are separated by tight junctions that prevent the movement of substances between the apical and basolateral surfaces, maintaining the polarization of the cell. Furthermore, the plasma membrane's structure is a phospholipid bilayer with hydrophilic surfaces and a hydrophobic interior, with different proteins embedded in each region according to their functions.
Understanding the differences between the apical and basolateral membranes is essential for comprehending how epithelial cells maintain their polarity and perform specific functions such as selective absorption and secretion of substances.