Which type of cell is characterized by having no membrane-bound organelles?

Bacterial cells are characterized by having no membrane-bound organelles, distinguishing them from plant, animal, and fungal cells. In bacterial cells, the structures necessary for life processes, such as the ribosomes, DNA, and cytoplasm, are present but not enclosed in membranes like they are in eukaryotic cells (plant, animal, and fungi). This absence of membrane-bound organelles is a defining feature of prokaryotic organisms, which include bacteria.

In contrast, plant and animal cells, both examples of eukaryotic cells, contain various organelles such as the nucleus, mitochondria, and endoplasmic reticulum, all enclosed by membranes. Fungi cells also share this characteristic of having membrane-bound organelles. Thus, the key distinction in bacterial cells is their simplicity and lack of these compartmentalized structures, allowing for a direct interaction of cellular components within their cytoplasm.