Nucleus – Structure And Function Practice Test

Nuclear pore complexes are the gateways that regulate traffic between the nucleus and the cytoplasm. The nucleus needs many of these gateways to move large molecules like RNA and ribosomal subunits out and various proteins in, so the nuclear envelope is studded with numerous pores. In a typical eukaryotic cell nucleus, the surface area of the envelope and the demand for fast, selective transport lead to a count in the thousands. Estimates commonly place the number around two thousand, which balances the need for efficient exchange with the physical limits of assembling and maintaining such complexes. If there were only a handful of pores, transport would bottleneck; if there were tens of thousands, the envelope would carry an unrealistically dense array of gateways. So the best approximation for a typical nucleus is about two thousand.