# Explain how the structure of the nucleus is related to its role in controlling cell activity.

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

## Mark scheme (4 marks)

1. The nuclear envelope is a double membrane that encloses the nucleus, separating transcription from translation and protecting DNA from damage by cytoplasmic enzymes.
2. Nuclear pores in the nuclear envelope allow selective passage of molecules such as mRNA and proteins between the nucleus and cytoplasm, enabling the nucleus to regulate gene expression.
3. The nucleus contains DNA organised into chromosomes, which carry genes that code for proteins; by controlling which genes are transcribed, the nucleus determines the proteins produced and therefore cell activity.
4. The nucleolus within the nucleus synthesises ribosomal RNA (rRNA) and assembles ribosome subunits, which are then exported through nuclear pores to carry out protein synthesis in the cytoplasm.

## Related

- [Revision notes for IB DP Biology Standard Level (2023 syllabus)](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
- [Practice this with AI marking (free)](https://www.gradenine.co.uk/start)

---
Source: [GradeNine](https://www.gradenine.co.uk/q/explain-how-the-structure-of-the-5eb27004) · Published by Druglandscape Ltd.