Skip to content
IGCSEBiology
Trial Class

Original practice · 5 questions · 16 marks · about 18 minutes

Diffusion and Concentration Gradient Practice Questions

Biology editorial review is supported by the named review panel. Reviewer participation may vary by guide. Checked against Cambridge IGCSE Biology 0610 (2026–2028); last reviewed August 2026.

These questions test your understanding of diffusion as a passive process, the role of concentration gradients, and real biological examples.

Before you open the answers

  • Attempt every question without notes.
  • Show working for calculations and write complete biological statements.
  • Use the suggested time as a guide, not a strict limit on the first attempt.

These are original practice questions. They do not reproduce an official Cambridge paper or official mark scheme.

  1. Question 1

    Paper 2 Both 3 marks Difficulty 2/5

    Define diffusion and give one example of diffusion in the human body.

    Show model answer and marking guidance
    1. Diffusion is the net movement of molecules or ions.
    2. From a region of higher concentration to a region of lower concentration.
    3. Example: oxygen diffusing from alveoli into blood capillaries (or any valid example).

    Watch for: Forgetting to say "net" movement: individual molecules move in all directions.

  2. Question 2

    Paper 4 Extended 4 marks Difficulty 3/5

    State four factors that affect the rate of diffusion.

    Show model answer and marking guidance
    1. Concentration gradient: steeper gradient increases rate.
    2. Temperature: higher temperature increases kinetic energy of molecules.
    3. Surface area: larger area allows more molecules to cross.
    4. Distance / thickness of membrane: shorter distance increases rate.

  3. Question 3

    Paper 4 Both 3 marks Difficulty 3/5

    Explain why diffusion is described as a passive process.

    Show model answer and marking guidance
    1. Passive means it does not require energy / ATP from the cell.
    2. Molecules move due to their own kinetic energy / random motion.
    3. Movement is down the concentration gradient: no energy input needed.

  4. Question 4

    Paper 2 Core 2 marks Difficulty 1/5

    A drop of ink is placed in a beaker of still water. Describe what happens and name the process.

    Show model answer and marking guidance
    1. The ink gradually spreads out / disperses through the water until evenly distributed.
    2. This is diffusion.

  5. Question 5

    Paper 4 Extended 4 marks Difficulty 4/5

    In the lungs, oxygen diffuses from the alveoli into the blood. Explain three features of the alveoli that increase the rate of this diffusion.

    Show model answer and marking guidance
    1. Large total surface area (many alveoli): more area for gas exchange.
    2. Thin walls (one cell thick): short diffusion distance.
    3. Rich blood supply: maintains a steep concentration gradient by carrying oxygen away.
    4. Moist lining: gases dissolve before diffusing across.

Mark the set consistently

Award a point only when the idea is clearly present in the written answer. Correct any missed point in a complete sentence, then test the same skill on a different question several days later.

Review the related teaching