What distinguishes eukaryotic cells from prokaryotic cells?

Eukaryotic cells are characterized by the presence of a defined nucleus, which is a distinct membrane-bound organelle that houses the cell's genetic material. This contrasts with prokaryotic cells, which lack a nucleus and have their DNA dispersed throughout the cytoplasm in a region called the nucleoid. The defined nucleus in eukaryotic cells allows for more complex regulation of gene expression and more sophisticated cellular processes, contributing to the overall complexity of eukaryotic organisms, such as animals, plants, and fungi.

While the absence of membrane-bound organelles is typical of prokaryotic cells, eukaryotic cells actually contain various organelles, such as mitochondria and the endoplasmic reticulum. Additionally, eukaryotic cells tend to be larger and more complex in structure compared to prokaryotic cells, which are generally smaller and simpler. Thus, the defining feature that distinguishes eukaryotic from prokaryotic cells is indeed the presence of a defined nucleus.