What distinguishes prokaryotic cells from eukaryotic cells?

Prokaryotic cells are distinct from eukaryotic cells primarily due to their lack of a nucleus. In prokaryotes, such as bacteria and archaea, genetic material is organized in a single circular DNA molecule that resides in a region called the nucleoid, instead of being enclosed within a membrane-bound nucleus as seen in eukaryotic cells. This fundamental difference is a key characteristic that helps define the two types of cells.

The absence of a membrane-bound nucleus in prokaryotic cells leads to simpler cellular structures and fewer organelles compared to eukaryotic cells. This distinction is crucial for understanding cellular biology and the evolution of life, as it reflects significant differences in cell organization and function.

The other options do not correctly capture the defining features of prokaryotic versus eukaryotic cells: prokaryotic cells do not have linear DNA, eukaryotic cells do have a cell membrane, and both cell types can reproduce asexually depending on the organism and conditions. These nuances emphasize the importance of recognizing the nucleus as a defining feature of eukaryotic cells.