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IB Biology SL B2.1.3 Simple Diffusion Questions

Explain how random kinetic motion drives oxygen or carbon-dioxide diffusion down a concentration gradient, and predict how gradient size changes the rate in IB Biology SL B2.1.3.

Syllabus
First assessment 2025
Course
Biology SL
Level
SL

Exam points

  • Define simple diffusion as passive net movement of particles down a concentration gradient using random kinetic motion, without ATP or transport proteins.
  • Explain how a steeper concentration gradient increases the rate of simple diffusion until net movement stops at equilibrium.
  • Identify small non-polar molecules such as oxygen and carbon dioxide that cross directly through the phospholipid bilayer by simple diffusion.

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Study B2.1.3—Simple diffusion conceptsOpen the corresponding Concept lesson for explanations, examples and exam connections.

IB Biology SL B2.1.3 Simple Diffusion Questions question 1

[Maximum number: 2]

Outline how molecules move across a membrane by simple diffusion.

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