AQA GCSE Biology

Diffusion, osmosis & active transport

AQA GCSE Biology revision on Diffusion, osmosis & active transport. Aligned to the AQA GCSE Biology 8461 specification. This bank has 25 practice questions on this topic.

Sample questions (3 of 25)

  1. Question 1

    Which process moves substances AGAINST a concentration gradient?

    • A) Diffusion
    • B) Osmosis
    • C) Active transport
    • D) Filtration
    Show answer

    Answer: Active transport

    Diffusion and osmosis move down a concentration gradient (high -> low) and need no energy. Active transport moves up the gradient (low -> high) and requires ATP from respiration. Root hair cells use it to absorb minerals.

  2. Question 2

    Osmosis is the movement of which substance?

    • A) Glucose
    • B) Water
    • C) Oxygen
    • D) Carbon dioxide
    Show answer

    Answer: Water

    Water moves from a dilute solution (high water concentration) to a concentrated solution (low water concentration) through a partially permeable membrane. The membrane lets water through but not the dissolved solute.

  3. Question 3

    Diffusion happens because particles...

    • A) Are attracted to each other
    • B) Move randomly and spread from high to low concentration
    • C) Get sucked towards membranes
    • D) Are pushed by air pressure
    Show answer

    Answer: Move randomly and spread from high to low concentration

    All particles in fluids (gases, liquids) move randomly. If concentration is unequal, random motion means more particles move from the high-concentration area than the other direction - net flow down the gradient. Equilibrium = random motion continues but no net change. No energy needed - it's just statistics.

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