A2 1 2025-style kidney extended response · 6 marks
Explain how the counter-current multiplier in the loop of Henle allows a desert mammal with long loops of Henle to produce very concentrated urine.
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CCEA A2 Biology 2025 past paper and mark scheme
Summer 2025 is part of the current CCEA GCE Biology (2016) specification, so every question style in it is still examinable. The papers and mark schemes themselves are published by CCEA; BioCCEA is an independent study tool and is not endorsed by CCEA.
What you sit in A2 2025
A2 1: Physiology, Co-ordination and Control, and Ecosystems
A2 1 written paper (2 hours)
Homeostasis and the kidney, nervous transmission, muscle contraction, hormonal co-ordination, photosynthesis, respiration and ecosystems.
A2 1 topic list and exam focusA2 2: Biochemistry, Genetics and Evolutionary Trends
A2 2 written paper (2 hours)
Respiration and ATP, monohybrid and dihybrid inheritance, sex linkage, population genetics, natural selection, speciation and gene technology.
A2 2 topic list and exam focusA2 3: Practical Skills in A2 Biology
A2 3 practical booklet plus a written practical-skills paper (1 hour 15 minutes)
Designing valid investigations, precision and error, statistical treatment of biological data and evaluating limitations.
A2 3 topic list and exam focus
How to sit the 2025 paper properly
- 1Print the paper and sit it in one block, to time, with no notes. A paper done in pieces tells you nothing about your exam performance.
- 2Mark it with the official CCEA mark scheme in front of you and award a mark only where the scheme's point is actually made.
- 3Log every dropped mark by unit topic, not by question number, so patterns appear across papers.
- 4Rewrite the two worst answers in full, using mark-scheme wording, then re-mark them.
- 5Come back to the same paper three weeks later and redo only the questions you lost marks on.
Sit the A2 2025 style questions
Answer each one under exam conditions. Your wording is marked against every mark scheme point before the full-mark answer appears.
1/3
These questions are written in the style of the CCEA GCE Biology (2016) papers and are not reproduced from any live paper. CCEA owns the copyright in its question papers and mark schemes — always download the official paper and mark scheme from CCEA and use these worked answers alongside them. BioCCEA is an independent study tool and is not endorsed by CCEA.
Worked A2 2025 questions with mark schemes
Question styles that carried the most marks in the Summer 2025 papers, each with the full list of creditworthy mark scheme points, a model answer at full marks, and the marking point candidates most often missed.
A2 1 2025-style kidney extended response · 6 marks
Explain how the counter-current multiplier in the loop of Henle allows a desert mammal with long loops of Henle to produce very concentrated urine.
Command word: Explain — how to answer itMark scheme — 6 creditworthy points
- Na⁺ and Cl⁻ actively transported out of the ascending limb, which is impermeable to water
- Water potential of the medulla tissue fluid is lowered
- Descending limb is permeable to water, so water leaves by osmosis and the filtrate concentrates
- Counter-current flow multiplies the gradient down the medulla
- A longer loop means the gradient extends deeper and becomes more negative
- More water is reabsorbed from the collecting duct by osmosis, so urine is more concentrated
Full-mark answer
Sodium and chloride ions are actively transported out of the ascending limb, which is impermeable to water, lowering the water potential of the medulla tissue fluid. Because the descending limb is permeable to water, water leaves it by osmosis and the filtrate becomes more concentrated as it descends. The opposite flow in the two limbs sets up a counter-current multiplier that maintains a water potential gradient increasing in negativity down the medulla. In a desert mammal the loops are longer, so this gradient extends deeper into the medulla and reaches a more negative water potential. As the collecting duct passes back through that medulla, more water is reabsorbed by osmosis along the steeper gradient, so a smaller volume of much more concentrated urine is produced.
Examiner insight: The adaptation mark is only awarded if you link loop length to how negative the medulla water potential becomes — not simply 'longer loop means more water reabsorbed'.
A2 1 2025-style nephron data question · 4 marks
Using the data on filtrate composition at three points in the nephron, explain the changes in glucose and urea concentration.
Command word: Explain — how to answer itMark scheme — 4 creditworthy points
- Glucose falls to zero by the end of the proximal convoluted tubule
- Because all glucose is selectively reabsorbed by active transport / co-transport with sodium
- Urea concentration rises along the nephron
- Because water is reabsorbed while urea is not (or is reabsorbed far more slowly), so urea becomes more concentrated
Full-mark answer
Glucose is present in the glomerular filtrate but falls to zero by the end of the proximal convoluted tubule, because it is all selectively reabsorbed by co-transport with sodium ions into the epithelial cells and then into the blood. Urea concentration rises along the nephron even though urea is not being added, because water is continuously reabsorbed from the filtrate while urea is not reabsorbed to any significant extent, so the same amount of urea is present in a smaller volume and its concentration increases.
Examiner insight: The urea mark depends on stating that the amount of urea does not change — it is concentration that rises because of water removal. This is the classic data-interpretation trap.
A2 1 2025-style graph interpretation, limiting factors · 6 marks
The graph shows the rate of photosynthesis of a crop plant at two carbon dioxide concentrations as light intensity increases. Explain the shape of both curves and identify the limiting factor at each stage.
Command word: Identify — how to answer itMark scheme — 6 creditworthy points
- At low light intensity both curves rise steeply and are the same / light intensity is the limiting factor
- More light means more photolysis of water, so more ATP and reduced NADP are produced for the light-independent reaction
- Each curve then levels off / plateaus, so light is no longer limiting
- At the plateau of the lower curve carbon dioxide concentration is the limiting factor
- Less CO2 means less GP formed from RuBP, so less TP and less carbohydrate
- The higher CO2 curve plateaus at a greater rate, showing another factor (temperature / enzyme concentration, e.g. rubisco) is then limiting
Full-mark answer
At low light intensities the two curves are identical and rise steeply, so light intensity is the limiting factor: as light increases, more water is photolysed and more ATP and reduced NADP are supplied to the light-independent reaction. Each curve then levels off, showing that light is no longer limiting. The lower curve plateaus at a lower rate because carbon dioxide concentration is now limiting - less carbon dioxide is fixed by RuBP, so less GP and therefore less triose phosphate and carbohydrate are made. The curve at the higher carbon dioxide concentration plateaus at a greater rate, and at that plateau some other factor such as temperature, and therefore the activity of rubisco, must be limiting.
Examiner insight: Naming the limiting factor is only half of each mark - you must say what that factor does inside the reaction. Answers that never mention ATP, reduced NADP, RuBP or GP rarely score above 3.
These questions are written in the style of the CCEA GCE Biology (2016) papers and are not reproduced from any live paper. CCEA owns the copyright in its question papers and mark schemes — always download the official paper and mark scheme from CCEA and use these worked answers alongside them. BioCCEA is an independent study tool and is not endorsed by CCEA.
Download the official CCEA paper and mark schemePractise the A2 2025 paper in the app
These open BioCCEA with A2 already selected, so you can sit questions in this paper's style and have them marked against the CCEA mark scheme.
Get your 2025 answers marked
Photograph a written answer from this paper and see it marked line by line in CCEA mark-scheme language, with the exact phrase you needed to earn each missing mark.