Biology 0610 · syllabus 3
Cambridge IGCSE Biology 0610 — Movement into and out of cells topical past papers
Diffusion, osmosis and active transport: how substances cross cell membranes, the factors that speed diffusion, and why plant cells turn turgid or flaccid.
- Questions
- 405
- Years
- 2009–2026
- With mark scheme
- 100%
- Questions 2022–2026
- 160
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What Movement into and out of cells covers
Substances cross cell membranes in three ways. Diffusion is the net movement of particles from where they are more concentrated to where they are less concentrated, caused by the particles' own random movement, so the cell spends no energy on it. Oxygen and carbon dioxide cross the walls of the alveoli this way, and pass into and out of leaves through the stomata. Diffusion is faster with a larger surface area, a steeper concentration gradient, a higher temperature and a shorter distance to travel, and investigating these factors, often with agar blocks containing an indicator, is a standard practical.
Osmosis is the diffusion of water through a partially permeable membrane, such as a cell membrane or dialysis tubing. A plant cell in pure water takes in water and swells until its cell wall resists; the water pressing outwards on the wall makes the cell firm, and firm cells hold up a non-woody plant. In a concentrated solution the cell loses water. Extended candidates explain these results with water potential — water moves from a dilute solution, with a higher water potential, to a concentrated one, with a lower water potential — and the terms turgid, turgor pressure, flaccid and plasmolysed, the last describing a cell whose membrane and cytoplasm have pulled away from the wall. An animal cell has no wall, so a red blood cell in water swells and bursts.
Active transport moves particles against their concentration gradient, from a lower concentration to a higher one, using energy released by respiration. Extended candidates add that protein carriers in the membrane do the moving, and use root hair cells as the example: they take up mineral ions from soil water that holds fewer of them than the cell does. Questions often ask for the percentage change in mass of plant tissue placed in a range of solutions, and these ideas return in gas exchange, absorption in the small intestine, water uptake by roots and the effect of the cholera toxin.
In the syllabus
The headings this topic has in the Cambridge International 2026–2028 syllabus, as the board prints them.
- 3 Movement into and out of cells
- 3.1 Diffusion
- 3.2 Osmosis
- 3.3 Active transport
What you should be able to do
- Define diffusion, osmosis and active transport, stating the direction of movement and whether energy from respiration is needed
- Explain how surface area, temperature, concentration gradient and distance affect the rate of diffusion
- Describe what happens to plant tissue and to animal cells in solutions more and less concentrated than their contents
- Calculate percentage change in mass, and read from a graph the concentration at which tissue neither gains nor loses mass
- Use the terms water potential, turgid, turgor pressure, flaccid and plasmolysis correctly (Extended)
- Explain why root hair cells need active transport and protein carriers to take up ions (Extended)
Key ideas
- Diffusion: net movement down a concentration gradient by the random movement of particles, with no energy needed from the cell
- Osmosis: water crossing a partially permeable membrane from a dilute solution to a more concentrated one, that is, from higher to lower water potential
- Active transport: movement against a concentration gradient, using energy released by respiration
- Percentage change in mass = (final mass − starting mass) ÷ starting mass × 100; a loss gives a negative value
- A cellulose cell wall stops a plant cell bursting in water; an animal cell has no wall and can burst
How Movement into and out of cells has been examined
From 2022 to 2026, Movement into and out of cells was on Paper 6 · Alternative to Practical in 10 of 14 exam series, worth about 21% of that paper’s marks.
| Paper | Questions | Share of marks | Series |
|---|---|---|---|
| Paper 1 · Multiple Choice (Core) | 67 | 5% | 14 of 14 |
| Paper 2 · Multiple Choice (Extended) | 49 | 4% | 14 of 14 |
| Paper 3 · Theory (Core) | 18 | 7% | 10 of 14 |
| Paper 4 · Theory (Extended) | 12 | 6% | 7 of 14 |
| Paper 6 · Alternative to Practical | 14 | 21% | 10 of 14 |
Momentum’s own count, over the questions in its bank for these years: a series is one exam session, every zone included, and a question filed under two chapters counts in both. Median marks per question: 1.
Filed in Momentum under: Movement in and Out of Cells.
A worked example
A potato cylinder has a mass of 2.50 g. After 30 minutes in a sucrose solution its mass is 2.15 g. Calculate the percentage change in mass and explain it.
- Change in mass = final mass − starting mass = 2.15 g − 2.50 g = −0.35 g
- Percentage change = −0.35 ÷ 2.50 × 100 = −14%
- Always divide by the starting mass, not the final mass
- The negative value is a loss: the solution was more concentrated than the cell contents, so it had a lower water potential, and water left the cells by osmosis
Answer: −14%: the cylinder lost water by osmosis to a solution with a lower water potential than its cells
Written by Momentum for this page, with its own numbers; it is not taken from a past paper.
Mistakes that cost marks
- Writing 'water moves from a high to a low concentration' without saying of what — say water moves from the dilute solution to the concentrated one, or from higher to lower water potential, because 'high concentration' could mean of solute
- Saying a plant cell bursts in pure water — its cell wall stops it, so it becomes turgid; only cells without a wall, such as red blood cells, burst
- Saying sugar or salt moves by osmosis — osmosis is only ever the movement of water; a solute that crosses a membrane does so by diffusion or active transport
- Comparing raw changes in mass when the pieces started at different masses — percentage change makes them comparable
- Describing active transport as fast diffusion — it moves particles the opposite way, against the gradient, and stops when respiration stops, for example when there is no oxygen
Exam technique
- In osmosis explanations, name the membrane as partially permeable, compare the water potentials or concentrations on each side, and give the direction water moves — these are often separate marks
- When describing results, quote figures with units from the table or graph, including negative values for losses
- To find where tissue neither gains nor loses water, read the concentration where the line crosses zero percentage change, and say that the cell contents have the same water potential, or concentration, as that solution
- In plans, cut pieces of the same size and shape from the same tissue, blot them dry before each weighing, and leave them long enough to change measurably
Practising in Momentum
- Every question in a chapter as one list, from every paper and year in the bank, newest first or shuffled.
- Each question turns over to its own part of the mark scheme, where the board published one.
- Narrow by paper, year, session, zone and marks, and star the questions worth keeping.
- Pick chapters, a number of questions and a time, and the exam builder draws a mock to sit and mark.
Past-paper questions and mark schemes are the copyright of Cambridge International. Momentum shows them to signed-in learners for revision and does not publish them on these pages.