Explain how the compartmentalisation provided by membrane-bound organelles benefits the eukaryotic cell.

IB DP Biology Standard Level (2023 syllabus) — B2.2 Organelles and compartmentalisation · Explain · 4 marks · View as Markdown

Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).

Model answer (4 marks)

Membrane‑bound organelles create separate compartments that maintain distinct internal environments (e.g. different pH or ion concentrations) within the same cell.

This separation allows enzymes and their substrates to be concentrated together, increasing the rate and efficiency of metabolic reactions.

It prevents potentially harmful enzymes, such as the hydrolytic enzymes in lysosomes, from damaging other cell components.

Separate compartments also enable different, incompatible metabolic pathways to occur simultaneously within the same cell without interfering with each other.

Examiner tips

Use the word ‘compartmentalisation’ and mention ‘membrane‑bound organelles’.
Show each benefit as a separate point, matching the four mark‑scheme items.
Include examples (lysosome, pH differences) to demonstrate understanding.
Keep sentences concise and use correct UK spelling (e.g. ‘organelles’, ‘compartmentalisation’).

Common mistakes

Confusing cytoplasm with organelles; forgetting that the cytosol is not membrane‑bound.
Lacking specific examples such as lysosomes or pH differences.
Writing a single long paragraph instead of separate points.

Mark scheme (4 marks)

Membranes create separate compartments that maintain distinct internal environments (e.g. different pH or ion concentrations) within the same cell.
This allows enzymes and substrates to be concentrated together, increasing the rate/efficiency of metabolic reactions.
Compartmentalisation prevents potentially harmful enzymes (e.g. hydrolytic enzymes in lysosomes) from damaging other cell components.
Separate compartments allow different, incompatible metabolic pathways to occur simultaneously within the same cell without interfering with each other.

Key terms in this question

compartmentalisation · membrane-bound organelle