IGCSE Biology: Movement into and out of Cells Practice Questions
Substances enter and leave cells by diffusion, osmosis and active transport. Diffusion and osmosis are passive and move substances down a concentration gradient, while active transport uses energy from respiration to move substances against their gradient.
Topic 3 of Cambridge IGCSE Biology 0610 is heavily tested because it explains almost every transport process later in the course. The marks sit in the exact wording of the definitions and in the ability to apply them to experimental data on potato cylinders or Visking tubing. The questions below cover both the definitions and the application.
What you need to know for Movement into and out of Cells
- DiffusionThe net movement of particles from a region of higher concentration to a region of lower concentration, down a concentration gradient, as a result of their random movement.
- OsmosisThe net movement of water molecules from a region of higher water potential, a dilute solution, to a region of lower water potential, a concentrated solution, through a partially permeable membrane.
- Active transportThe movement of particles through a cell membrane from a region of lower concentration to a region of higher concentration, using energy from respiration and carrier proteins in the membrane.
- Plant cells in solutionsIn a dilute solution a plant cell takes in water and becomes turgid. In a concentrated solution it loses water, becomes flaccid, and eventually the cell membrane pulls away from the cell wall, which is plasmolysis.
- Animal cells in solutionsAnimal cells have no cell wall. In a dilute solution they swell and may burst. In a concentrated solution they lose water and shrink.
- Factors affecting the rate of diffusionSurface area, distance, temperature and the steepness of the concentration gradient. A larger surface area, a shorter distance, a higher temperature and a steeper gradient all increase the rate.
IGCSE Biology Movement into and out of Cells questions and answers
4 exam-style questions written to the 0610 syllabus. Try each one on paper first, then open the worked answer to check your method against the marks.
Define osmosis.
Show the worked answer
- State that it is the net movement of water molecules specifically, not of any particle.
- State the direction: from a region of higher water potential, meaning a dilute solution, to a region of lower water potential, meaning a more concentrated solution.
- State that it happens through a partially permeable membrane.
- Together: osmosis is the net movement of water molecules from a region of higher water potential to a region of lower water potential through a partially permeable membrane.
A cylinder of potato is left in a concentrated sucrose solution for one hour. Its mass decreases. Explain this result.
Show the worked answer
- The sucrose solution is more concentrated than the cell sap inside the potato cells, so it has a lower water potential.
- The cell membrane is partially permeable, allowing water molecules through but not sucrose.
- Water therefore moves out of the potato cells into the solution by osmosis, down the water potential gradient.
- Loss of water from the cells reduces the mass of the cylinder, and the cells become flaccid and may plasmolyse.
Compare diffusion and active transport. Give two differences.
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- Difference 1, direction: diffusion moves particles down a concentration gradient, from high to low. Active transport moves particles against the gradient, from low to high.
- Difference 2, energy: diffusion is passive and requires no energy from the cell. Active transport requires energy released by respiration.
- A third acceptable difference is that active transport requires carrier proteins in the membrane, whereas diffusion does not.
- Each difference must be stated for both processes to score.
Root hair cells contain a large number of mitochondria. Explain why.
Show the worked answer
- Mineral ions in soil water are usually at a lower concentration than inside the root hair cell.
- The cell therefore has to absorb them by active transport, against the concentration gradient.
- Active transport requires energy.
- Mitochondria are the site of aerobic respiration, which releases that energy, so a cell carrying out a lot of active transport contains many of them.
Common mistakes in this topic
- Defining osmosis without mentioning the partially permeable membrane.
- Saying water moves from high concentration to low concentration without specifying whether you mean concentration of water or of solute. Use water potential or say dilute to concentrated.
- Confusing turgid with plasmolysed. Turgid is full of water. Plasmolysed has lost so much water that the membrane pulls away from the wall.
- Forgetting that animal cells burst in dilute solutions because they have no cell wall.
- Writing that active transport happens by diffusion through carrier proteins. Carrier proteins are used, but energy is required and the movement is against the gradient.
Exam tips
- Memorise the three definitions word for word. They appear on nearly every paper and are pure marks.
- In any experiment question, work out which solution is more concentrated first. Everything else follows from that.
- Percentage change in mass equals change in mass divided by starting mass, multiplied by 100. Use percentage change so cylinders of different starting mass can be compared.
- When a graph crosses the x-axis in a potato experiment, that concentration equals the water potential of the cell sap. Say so.
- Always name the gradient you are talking about: concentration gradient for diffusion, water potential gradient for osmosis.
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Movement into and out of Cells FAQs
What is the difference between diffusion and osmosis?
Diffusion is the net movement of any particles from a higher to a lower concentration. Osmosis is a special case that applies only to water molecules and only through a partially permeable membrane, moving from a dilute solution to a more concentrated one. All osmosis is diffusion of water, but not all diffusion is osmosis.
Why do plant cells not burst in pure water?
A plant cell takes in water by osmosis and swells, but the strong cellulose cell wall resists further expansion and pushes back on the contents. The cell becomes turgid and firm rather than bursting. Animal cells have no cell wall, which is why they can burst in the same conditions.
What is plasmolysis?
Plasmolysis is what happens when a plant cell loses so much water by osmosis that the cytoplasm shrinks and the cell membrane pulls away from the cell wall. It occurs when the cell is placed in a solution more concentrated than its own cell sap, and the cell becomes flaccid before plasmolysing.
Does active transport happen in both plants and animals?
Yes. Root hair cells use active transport to absorb mineral ions from dilute soil water, and cells lining the small intestine use it to absorb glucose and amino acids when their concentration in the gut is lower than in the blood. Both processes need energy released by respiration.
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Written to the published Cambridge IGCSE Biology (0610) syllabus. Check your school entry code and syllabus year, because Core and Extended candidates are assessed on different content. Last reviewed 2026-08-12.