The primary difference between a prokaryotic cell and a eukaryotic cell lies in their cellular structure. Prokaryotic cells lack a true nucleus and membrane-bound organelles, with their genetic material dispersed throughout the cytoplasm. In contrast, eukaryotic cells possess a defined nucleus and various organelles, allowing for greater complexity and specialization. Prokaryotes are generally unicellular (like bacteria), while eukaryotes can be unicellular or multicellular (like plants and animals). This fundamental difference significantly influences their functions and processes.