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Practice · Biology · 2025 syllabus · C2.2

IB Biology C2.2 Neural signalling: practice questions

5 exam-style questions on C2.2 Neural signalling, SL and HL, 2 marked HL: 3 multiple choice, 1 data-based 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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C2.2-01 · Paper 1A style · multiple choice · 1 mark

Pumping for the resting potential

How do sodium-potassium pumps help to establish the resting potential of a neuron? [1]

  1. They move two Na+ out and three K+ in by facilitated diffusion.
  2. They use ATP to move three Na+ out and two K+ in.
  3. They use ATP to move three K+ out and two Na+ in.
  4. They open to let Na+ diffuse in until the inside becomes positive.
Show the answer and the reasoning

Answer: B. B is correct. Each cycle of the pump uses one ATP to move three sodium ions out and two potassium ions in, against their concentration gradients. More positive charge leaves than enters, and together with potassium leaking out through channels this makes the inside negative (about −70 mV). A is wrong twice: pumping is active transport, not facilitated diffusion, and the numbers are reversed. C reverses the directions of the two ions. D describes depolarisation during an action potential, through voltage-gated channels, not the pump.

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The 5 questions in C2.2

  1. C2.2-01 Pumping for the resting potentialPaper 1A style · multiple choice · 1 mark
  2. C2.2-02 Impulse frequency from a tracePaper 1A style · multiple choice · 1 mark · HL
  3. C2.2-03 Cocaine and neonicotinoids comparedPaper 1A style · multiple choice · 1 mark · HL
  4. C2.2-04 Events at a synapsePaper 2 style · short answer · 7 marks
  5. C2.2-05 Axon diameter and conduction speedPaper 1B style · data-based · 9 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.