What typically characterizes prokaryotic cells?

Prokaryotic cells are primarily characterized by the lack of membrane-bound organelles. This means that structures such as the nucleus, mitochondria, and endoplasmic reticulum, which are found in eukaryotic cells, are absent in prokaryotes. Instead of a nucleus, prokaryotic cells have a region called the nucleoid, where their genetic material is located in a concentrated area but not enclosed within a membrane. This fundamental difference is one of the key distinguishing features of prokaryotic cells and greatly influences their structure, function, and overall biology.

The other options, while they may apply to some organisms, do not define prokaryotic cells. For instance, the presence of a nucleus is characteristic of eukaryotic cells, not prokaryotes. While some prokaryotic organisms, such as certain bacteria, can photosynthesize, this ability is not a characteristic of all prokaryotes and doesn't define the group as a whole. Similarly, chloroplasts are specific to plant cells (eukaryotic) and are absent in prokaryotes. Thus, the distinguishing feature of prokaryotic cells rests on the absence of membrane-bound organelles.