Explain how the structure of the nuclear envelope is related to its function in a eukaryotic cell.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Model answer (4 marks)
The nuclear envelope is a double‑phospholipid bilayer that forms a physical barrier between the nucleus and cytoplasm.
Its two membranes contain nuclear pores, which allow selective transport of molecules such as mRNA and proteins.
The outer membrane is continuous with the rough endoplasmic reticulum, linking nuclear activity to protein synthesis.
By enclosing the DNA, the envelope protects it from cytoplasmic processes and permits transcription and translation to be spatially separated, enabling post‑transcriptional modification of mRNA before export.
Its two membranes contain nuclear pores, which allow selective transport of molecules such as mRNA and proteins.
The outer membrane is continuous with the rough endoplasmic reticulum, linking nuclear activity to protein synthesis.
By enclosing the DNA, the envelope protects it from cytoplasmic processes and permits transcription and translation to be spatially separated, enabling post‑transcriptional modification of mRNA before export.
Examiner tips
- Use the term ‘double‑phospholipid bilayer’ and ‘nuclear pores’ to show structure. Mention the continuity with rER to link structure to function. Explain the protective and spatial separation roles. Keep answer concise to fit 4 marks.
Common mistakes
- Confusing the nuclear envelope with the nuclear membrane. Forgetting to mention the selective transport function of nuclear pores. Over‑extending the answer with unrelated details such as chromatin structure.
Mark scheme (4 marks)
- The nuclear envelope consists of two phospholipid bilayer membranes (double membrane), which forms a physical barrier separating the nucleus from the cytoplasm.
- Nuclear pores are present in the nuclear envelope and allow selective transport of molecules (such as mRNA and proteins) between the nucleus and the cytoplasm.
- The outer membrane of the nuclear envelope is continuous with the rough endoplasmic reticulum (rER), linking nuclear activity to protein synthesis and processing.
- The double membrane / enclosed compartment protects DNA from potentially damaging cytoplasmic processes and allows transcription and translation to be spatially separated, enabling post-transcriptional modification of mRNA before export.
Key terms in this question
nuclear envelope · eukaryotic cell
Related
- All IB DP Biology Standard Level (2023 syllabus) revision notes →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →
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