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Practice · Biology · 2025 syllabus · B2.2

IB Biology B2.2 Organelles and compartmentalization: practice questions

4 exam-style questions on B2.2 Organelles and compartmentalization, SL and HL, 2 marked HL: 3 multiple choice and 1 short answer. Each one comes with the mark scheme, a model answer and the reasoning behind every mark. Free with your email.

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B2.2-01 · Paper 1A style · multiple choice · 1 mark · HL

Organelles adapted to function

Which statement correctly links a feature of an organelle to its function? [1]

  1. Thylakoids have a small internal volume, so a high concentration of protons can build up quickly.
  2. The inner mitochondrial membrane is smooth, so ATP synthase molecules are spread out evenly.
  3. Free ribosomes make proteins that are then packaged by the Golgi apparatus for secretion.
  4. The stroma holds the enzymes of the Krebs cycle together with their substrates.
Show the answer and the reasoning

Answer: A. A is correct. The fluid inside each thylakoid occupies a very small volume, so protons pumped into it quickly reach a high concentration, giving the steep gradient used to make ATP in photosynthesis. B is wrong because the inner mitochondrial membrane is folded into cristae, giving a large surface area for ATP synthase and the electron transport chain. C is wrong because proteins for secretion are made by ribosomes bound to the rough ER; free ribosomes make proteins that stay in the cell. D confuses two organelles: the stroma of the chloroplast holds the Calvin cycle enzymes, while Krebs cycle enzymes are in the mitochondrial matrix.

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The 4 questions in B2.2

  1. B2.2-01 Organelles adapted to functionPaper 1A style · multiple choice · 1 mark · HL
  2. B2.2-02 Why keep the nucleus separatePaper 1A style · multiple choice · 1 mark
  3. B2.2-03 Tracking a secreted proteinPaper 1A style · multiple choice · 1 mark · HL
  4. B2.2-04 Compartments in a phagocytePaper 2 style · short answer · 5 marks

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Every Biology and Chemistry question here is original, written for practice in the style of the papers set since the 2025 syllabus, with invented data. Developed independently from the International Baccalaureate Organization, which has not endorsed it. Found a mistake? Email vytis@limeadmissions.com with the question id.