Explain how the structure of the nuclear envelope is related to its function in regulating communication between the nucleus and the cytoplasm.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Model answer (4 marks)
The nuclear envelope is made of two phospholipid bilayer membranes (inner and outer) that form a physical barrier separating the genetic material from the cytoplasm.
Nuclear pores are protein‑lined channels in the envelope that allow selective passage of molecules between the nucleus and cytoplasm.
mRNA (and ribosomal subunits) can exit the nucleus through these pores, permitting gene expression to continue in the cytoplasm.
Proteins required in the nucleus (e.g. transcription factors, histones, DNA polymerase) are selectively imported through the pores from the cytoplasm, enabling regulation of nuclear activity.
Nuclear pores are protein‑lined channels in the envelope that allow selective passage of molecules between the nucleus and cytoplasm.
mRNA (and ribosomal subunits) can exit the nucleus through these pores, permitting gene expression to continue in the cytoplasm.
Proteins required in the nucleus (e.g. transcription factors, histones, DNA polymerase) are selectively imported through the pores from the cytoplasm, enabling regulation of nuclear activity.
Examiner tips
- Use the term ‘phospholipid bilayer’ and ‘protein‑lined channels’ to show understanding of structure. Mention both import and export to cover all functions. Keep each point brief but complete – 1 mark each.
Common mistakes
- Confusing the nuclear envelope with the nuclear membrane; they are the same but students sometimes use wrong terminology. Forgetting to mention selective import of proteins. Using vague terms like ‘membrane’ without specifying bilayer or pores.
Mark scheme (4 marks)
- The nuclear envelope consists of two phospholipid bilayer membranes (inner and outer), which forms a physical barrier that separates the genetic material from the cytoplasm.
- Nuclear pores are protein-lined channels in the nuclear envelope that allow selective passage of molecules between the nucleus and cytoplasm.
- mRNA (and ribosomal subunits) can exit the nucleus through nuclear pores, allowing gene expression to proceed in the cytoplasm.
- Proteins required in the nucleus (e.g. transcription factors, histones, DNA polymerase) are selectively imported through the nuclear pores from the cytoplasm, enabling regulation of nuclear activity.
Key terms in this question
Related
- All IB DP Biology Standard Level (2023 syllabus) revision notes →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →
More Organelles and compartmentalisation questions
- Explain how the compartmentalisation provided by membrane-bound organelles allow…
- Explain how the structure of the mitochondrion is related to its function in aer…
- Explain how the structure of the chloroplast is related to its function in photo…
- Explain how the structure of the lysosome is related to its function in intracel…
- Explain how the compartmentalisation provided by membrane-bound organelles benef…
- Explain how the structure of the smooth endoplasmic reticulum (sER) is related t…