Here's why:

* It's a fundamental structure: The nuclear membrane is the membrane that encloses the nucleus of a cell. The nucleus houses the cell's genetic material (DNA), which is essential for all cellular processes.

* All eukaryotic cells have a nucleus: Plant and animal cells are both eukaryotic cells, meaning they have a true nucleus. Therefore, both types of cells have a nuclear membrane.

Let me know if you have any other questions!