Final answer:
In eukaryotic cells, the inner nuclear membrane is lined by a fibrous layer of proteins known as the nuclear lamina, which provides structural support to the nucleus and helps in organizing the cell's genetic material.
Step-by-step explanation:
In most eukaryotic cells, the inner nuclear membrane of the cell is lined by a fibrous layer of proteins called the nuclear lamina. The nucleus is an essential organelle that houses the genetic material of the cell in the form of DNA. It is enclosed by the nuclear envelope, a double-membrane structure consisting of an inner and an outer lipid bilayer.
The nuclear envelope is distinct from other cellular membranes due to the presence of nuclear pores, which are intricate protein complexes allowing the regulated movement of substances between the nucleus and the cytoplasm. The nuclear lamina is a mesh-like network of protein fibers that provides structural support to the nucleus and plays a critical role in organizing the genetic material within.
The overall function of the nuclear envelope, with its associated structures like the nuclear pores and the nuclear lamina, is to safeguard the genetic material and regulate its access to the rest of the cell. Answering the student's question, the fibrous layer of proteins lining the inner nuclear membrane is called the nuclear lamina, which is the correct option in this context, hence the answer is: 4) lamina.