You would expect to find a membrane-enclosed nucleus in eukaryotic cells.

Here's why:

* Eukaryotic cells are complex cells that have a true nucleus, which is a membrane-bound organelle containing the cell's genetic material (DNA). This nucleus helps to protect and organize the DNA.

* Prokaryotic cells are simpler cells that lack a membrane-bound nucleus. Their DNA is located in a region called the nucleoid, which is not enclosed by a membrane.

So, if you're looking for a cell with a nucleus surrounded by a membrane, you're looking for a eukaryotic cell.