Q.What are nuclear pores? State their function.

The nucleus is bounded by a nuclear envelope made of two parallel membranes, with a narrow perinuclear space between them. At many points, however, this envelope is not continuous: the two membranes fuse together, creating minute openings called nuclear pores.

• Nuclear pores are the small pore-like interruptions in the nuclear envelope, formed wherever its two membranes join.
• Their function is to act as passageways between the nucleus and the cytoplasm.
• Through them, RNA and protein molecules move in both directions — into and out of the nucleus. …

Under the electron microscope the nucleus is seen to be enclosed by a nuclear envelope built of two parallel membranes. Between these two membranes lies a gap called the perinuclear space, roughly ten to fifty nanometres wide. This double-membrane envelope acts as a barrier that separates the contents of the nucleus from the cytoplasm around it. If the barrier were completely sealed, though, the nucleus could not exchange anything with the rest of the cell — and that is where the nuclear pores come in.

At many points along the envelope the two membranes are not kept apart but fuse together. Each place where they fuse leaves a minute opening, and these openings are the nuclear pores. So a nuclear pore is essentially a channel through the otherwise continuous double membrane.

Their function follows directly from their position:

• They serve as passageways connecting the interior of the nucleus with the cytoplasm.
• Through these pores, RNA and protein molecules are able to move in both directions — outward from the nucleus into the cytoplasm and inward from the cytoplasm into the nucleus. …

Method: Locate the structure within its parent, then derive function from its position

For a "what is X, state its function" question about a sub-structure of a larger organelle (nuclear pores within the nuclear envelope), first place the structure precisely within its parent: what is it a modification of, and how is it physically formed (here, the fusion of the two nuclear membranes at specific points). Getting this positional detail right is what separates real understanding of the structure from a vague "it's a hole in the nucleus" answer. …