NSF Senior Science Bee Practice Exam 2025 - Free Science Bee Practice Questions and Study Guide

The correct choice identifies a fundamental distinction between prokaryotic and eukaryotic cells: prokaryotic cells lack a nucleus and organelles. In prokaryotic cells, which include bacteria and archaea, the genetic material is not enclosed within a membrane-bound nucleus. Instead, it is typically organized in a single circular DNA molecule located in a region called the nucleoid. This structural characteristic is a defining trait of prokaryotes.

Additionally, prokaryotic cells do not possess membrane-bound organelles such as mitochondria, chloroplasts, or the endoplasmic reticulum, which are hallmark features of eukaryotic cells. Eukaryotic cells, found in organisms such as plants, animals, and fungi, have a more complex organization with compartmentalized structures that separate various biochemical processes. This difference is essential for understanding the complexity and functionality of cellular processes in different life forms.

The other choices suggest misconceptions about cellular biology. For example, prokaryotic cells often do have a cell wall, usually composed of peptidoglycan, and eukaryotic cells can be unicellular or multicellular. Furthermore, eukaryotic cells are generally larger than prokaryotic cells,