Final answer:
Gut epithelial cells are characterized by a difference in protein composition between their apical and basolateral surfaces.
Step-by-step explanation:
Epithelial cells are characterized by the polarized distribution of organelles and membrane-bound proteins between their basal and apical surfaces. The membranes of the apical and basolateral domains are different in their protein composition. The apical surface of gut epithelial cells, for example, contains specific proteins that aid in secretion and absorption, such as digestive enzymes in the small intestine or mucous in respiratory tract lining cells.