A Level Biology Practice Exam

What is a defining feature of prokaryotic cells?

1. Lack of membrane-bound nucleus

2. Presence of membrane-bound organelles

3. Larger than eukaryotic cells

4. Capability to perform photosynthesis

The correct answer is: Lack of membrane-bound nucleus

A defining feature of prokaryotic cells is the lack of a membrane-bound nucleus. Instead of housing their genetic material within a defined nucleus, prokaryotes have their DNA located in a region called the nucleoid, which is not enclosed by a membrane. This characteristic differentiates prokaryotic cells, such as bacteria and archaea, from eukaryotic cells, which possess a well-defined nucleus and membrane-bound organelles. The presence of membrane-bound organelles is a feature of eukaryotic cells, not prokaryotic. Prokaryotic cells are generally smaller than eukaryotic cells, which makes the size comparison misleading in defining them. While some prokaryotes can perform photosynthesis, this ability is not exclusive to them and doesn’t serve as a defining feature, as many eukaryotes can also photosynthesize. Hence, the absence of a membrane-bound nucleus remains the most critical distinguishing trait.