Which organelle controls movement in or out of the nucleus?

• A. Centrioles
• B. Nuclear Membrane
• C. Vacuole
• D. Chloroplast

Answer: (B)

Movement into and out of the nucleus is controlled by the nuclear membrane, also called the nuclear envelope. It surrounds the nucleus and has nuclear pores that act as selective gates. Through these pores, necessary RNAs and ribosomal subunits exit to the cytoplasm, while proteins needed inside can enter, guided by signals and transport proteins. This gatekeeping keeps the nucleus protected while allowing essential communication with the rest of the cell. The other structures have different roles: centrioles organize spindle fibers during cell division, vacuoles store substances, and chloroplasts perform photosynthesis. They don’t regulate traffic across the nuclear boundary.