What is a key feature of eukaryotic cells?

A key feature of eukaryotic cells is that they have a membrane-bound nucleus. This is an essential characteristic that distinguishes eukaryotic cells from prokaryotic cells, which lack a defined nucleus. In eukaryotic cells, the genetic material is enclosed within the nuclear membrane, allowing for more complex regulation of gene expression and cellular processes.

The presence of the nucleus also allows for compartmentalization within the cell, where various cellular functions can occur in different areas, leading to greater efficiency and specialization. Additionally, eukaryotic cells often contain other membrane-bound organelles such as mitochondria, endoplasmic reticulum, and Golgi apparatus, further enhancing their complexity and functionality.

In contrast, options that suggest features such as being small and simple or lacking internal structures are characteristics of prokaryotic cells. Furthermore, the notion that eukaryotic cells are only found in bacteria is incorrect, as eukaryotic cells also make up fungi, plants, and animals. Therefore, the defining feature of having a membrane-bound nucleus is what categorizes these cells as eukaryotic.