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Practice · Biology · 2025 syllabus · B3.2

IB Biology B3.2 Transport: practice questions

6 exam-style questions on B3.2 Transport, SL and HL, 2 marked HL: 3 multiple choice, 1 data-based, 1 short answer and 1 extended response. Each one comes with the mark scheme, a model answer and the reasoning behind every mark. Free with your email.

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B3.2-01 · Paper 1A style · multiple choice · 1 mark

Capillaries built for exchange

Which feature of capillaries increases the rate of exchange of materials with the surrounding tissues? [1]

  1. A thick layer of elastic fibres in the wall
  2. Valves at intervals along their length
  3. A wide lumen that reduces resistance to flow
  4. A wall one cell thick, with pores in some tissues
Show the answer and the reasoning

Answer: D. D is correct. A wall only one cell thick gives the shortest possible diffusion distance, and in tissues where exchange must be very rapid (such as the kidney glomerulus or the villi of the small intestine) the cells have pores called fenestrations. A describes arteries, where elastic fibres stretch and recoil with each heartbeat. B describes veins, where valves stop backflow. C is wrong because capillaries have a very narrow lumen, only just wide enough for red blood cells; their narrowness and branching create the large total surface area.

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The 6 questions in B3.2

  1. B3.2-01 Capillaries built for exchangePaper 1A style · multiple choice · 1 mark
  2. B3.2-02 Sap flow before leaves openPaper 1A style · multiple choice · 1 mark · HL
  3. B3.2-03 Valves in the cardiac cyclePaper 1A style · multiple choice · 1 mark · HL
  4. B3.2-04 Arteries and veins comparedPaper 2 style · short answer · 7 marks
  5. B3.2-05 Cholesterol, smoking and heart diseasePaper 1B style · data-based · 9 marks
  6. B3.2-06 Movement of waterPaper 2 style · extended response · 15 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.