Microbiology Practice Exam

In terms of cellular organization, which structure is absent in prokaryotic cells?

1. Cell membrane

2. Cytoplasm

3. Nucleus

4. Cell wall

The correct answer is: Nucleus

Prokaryotic cells are characterized by their lack of a true nucleus, which is a defining feature that sets them apart from eukaryotic cells. Instead of having a membrane-bound nucleus, prokaryotes contain their genetic material in a region called the nucleoid, where the DNA is located within the cytoplasm but not enclosed by a membrane. This fundamental difference highlights the simpler structure of prokaryotic cells compared to eukaryotic cells, which have distinct organelles, including a nucleus that houses their DNA. In contrast, prokaryotic cells do possess a cell membrane, cytoplasm, and, in most cases, a cell wall, which are essential for their survival and functioning. The cell membrane is vital for regulating the movement of substances in and out of the cell, the cytoplasm contains the cellular components and facilitates metabolic processes, and the cell wall provides structural support and shape. Thus, the absence of a nucleus in prokaryotic cells is a crucial aspect of their cellular organization.