Domains of Life; Prokaryotic vs. Eukaryotic Cells

ID #1488

I can't distinguish the exact definitions between nucleoid and nucleus. I think the difference between them is the existence of a nuclear membrane. Both are regions, not exact things. So, the nucleoid is only for prokaryotes and the nucleus is only for eukaryotes. Am I right?

You're really close on this, but not quite there yet. The nucleus is actually an organelle, or what I believe you were referring to as an "exact thing." The nucleoid region is just a region of a prokaryotic cell where the genome resides. And yes, only eukaryotes have a nucleus, which is separated from the cytoplasm by a nuclear envelope (actually a double membrane, but we'll cover that later) -- that's the very definition of being a eukaryote!

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