# Explain how the structure of the nuclear envelope enables selective communication between the nucleus and the cytoplasm.

> IB DP Biology Higher Level (2023 syllabus) — A2.2 Cell structure · Explain · 4 marks

## Mark scheme (4 marks)

1. The nuclear envelope consists of two phospholipid bilayer membranes (inner and outer), which form a barrier separating the nucleoplasm from the cytoplasm.
2. Nuclear pore complexes span both membranes and act as selective channels, allowing regulated passage of molecules between nucleus and cytoplasm.
3. Large molecules such as mRNA and ribosomal subunits exit through nuclear pores, while proteins such as transcription factors and RNA polymerase are imported into the nucleus through the same pores.
4. The outer membrane of the nuclear envelope is continuous with the rough endoplasmic reticulum (rER), linking nuclear activity to protein synthesis and processing in the cytoplasm.

## Key terms

- [nuclear envelope](https://www.gradenine.co.uk/glossary/nuclear-envelope)

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Source: [GradeNine](https://www.gradenine.co.uk/q/explain-how-the-structure-of-the-4825e8f1) · Published by Druglandscape Ltd.