AAMC FL Practice Exam

What distinguishes prokaryotes from eukaryotes?

1. Presence of a nucleus

2. Ability to reproduce

3. Size of the organism

4. Respiration methods

The correct answer is: Presence of a nucleus

The presence of a nucleus is a fundamental distinction between prokaryotes and eukaryotes. Prokaryotes, which include bacteria and archaea, lack a true nucleus; instead, their genetic material is located in a region called the nucleoid, which is not membrane-bound. In contrast, eukaryotic cells, such as those in animals, plants, fungi, and protists, have a well-defined nucleus that houses their DNA and is surrounded by a nuclear membrane. This structural difference is a key characteristic that helps to categorize these two groups of organisms and influences their cellular functions and complexity. Other factors, like the ability to reproduce, size of the organisms, and respiration methods, do not serve as definitive distinguishing characteristics because both prokaryotes and eukaryotes can reproduce, vary widely in size, and utilize diverse methods of respiration. These traits do not delineate the two groups as clearly as the presence or absence of a nucleus does.