What structure surrounds and protects the nucleus?

The structure that surrounds and protects the nucleus is the nuclear envelope. This double membrane encases the nucleus and serves several important functions. Firstly, it acts as a barrier, controlling what substances can enter or exit the nucleus, thus maintaining an environment conducive to the proper functioning of genetic material. The nuclear envelope also has pores that allow for the regulated exchange of materials, such as RNA and proteins, between the nucleus and the cytoplasm. This selective permeability is crucial for the cell's ability to communicate and function effectively.

In contrast, other structures have different roles. The vacuole primarily functions as a storage organelle within plant and some animal cells, not protecting the nucleus. The cell membrane surrounds the entire cell, serving as a barrier and gatekeeper for substances entering and leaving the cell. The cell wall, found in plant cells and some other organisms, provides structural support and protection to the cell as a whole but does not specifically function to protect the nucleus. Thus, the nuclear envelope is the correct answer as it is specifically designed to envelop and safeguard the nucleus.