In a typical eukaryotic cell, what structure directly surrounds the nucleus and separates the nucleoplasm from the cytoplasm?

• A. The plasma membrane
• B. The nuclear envelope (double membrane with nuclear pore complexes)
• C. The nucleolus
• D. The cell wall

Answer: (B)

Verified step by step guidance

1. Identify the main compartments within a eukaryotic cell relevant to the question: the nucleus and the cytoplasm.
2. Recall that the nucleus is enclosed by a specialized double membrane structure that separates its internal environment (nucleoplasm) from the cytoplasm.
3. Understand that this double membrane is called the nuclear envelope, which contains nuclear pore complexes allowing selective exchange between the nucleus and cytoplasm.
4. Differentiate the nuclear envelope from other cell structures such as the plasma membrane (which surrounds the entire cell), the nucleolus (a substructure inside the nucleus), and the cell wall (found in plants and some other organisms, but not surrounding the nucleus).
5. Conclude that the structure directly surrounding the nucleus and separating nucleoplasm from cytoplasm is the nuclear envelope.