A2 1 2024-style synaptic transmission question · 6 marks
Describe the events at a cholinergic synapse when an action potential arrives at the presynaptic membrane.
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CCEA A2 Biology 2024 past paper and mark scheme
Summer 2024 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 2024
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 2024 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 2024 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 2024 questions with mark schemes
Question styles that carried the most marks in the Summer 2024 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 2024-style synaptic transmission question · 6 marks
Describe the events at a cholinergic synapse when an action potential arrives at the presynaptic membrane.
Command word: Describe — how to answer itMark scheme — 6 creditworthy points
- Depolarisation opens voltage-gated calcium ion channels in the presynaptic membrane
- Calcium ions diffuse in, causing vesicles to move to and fuse with the presynaptic membrane
- Acetylcholine is released by exocytosis into the synaptic cleft
- Acetylcholine diffuses across the cleft and binds to complementary receptors on the postsynaptic membrane
- Sodium ion channels open, sodium ions enter and depolarise the postsynaptic membrane; if threshold is reached a new action potential is generated
- Acetylcholinesterase hydrolyses acetylcholine so the response is not prolonged; products are reabsorbed
Full-mark answer
The arrival of the action potential depolarises the presynaptic membrane and opens voltage-gated calcium ion channels, so calcium ions diffuse into the presynaptic knob. This causes synaptic vesicles to move to and fuse with the presynaptic membrane, releasing acetylcholine into the synaptic cleft by exocytosis. Acetylcholine diffuses across the cleft and binds to complementary receptors on the postsynaptic membrane, opening sodium ion channels. Sodium ions enter and depolarise the postsynaptic membrane, and if the threshold is reached a new action potential is generated. Acetylcholinesterase in the cleft then hydrolyses the acetylcholine into choline and ethanoic acid, which are reabsorbed into the presynaptic knob, so the postsynaptic neurone is not continuously stimulated.
Examiner insight: The acetylcholinesterase point is worth a mark on its own and is the most frequently omitted. Say why it matters — to prevent continuous stimulation.
A2 1 2024-style explain question · 3 marks
Explain why transmission across a synapse occurs in one direction only.
Command word: Explain — how to answer itMark scheme — 3 creditworthy points
- Neurotransmitter (acetylcholine) is only made and stored in the presynaptic knob
- Receptors for the neurotransmitter are only present on the postsynaptic membrane
- So neurotransmitter can only diffuse from the presynaptic to the postsynaptic side and only bind there
Full-mark answer
Acetylcholine is synthesised and stored in vesicles only in the presynaptic knob, so it can only be released from that side of the cleft. The complementary receptors that bind acetylcholine are present only on the postsynaptic membrane. Neurotransmitter therefore diffuses only from the presynaptic to the postsynaptic membrane and can only produce a response there, so transmission is unidirectional.
Examiner insight: Two separate marks: where the neurotransmitter is, and where the receptors are. Answers giving only one of these cap at 2.
A2 2 2024-style homeostasis question · 6 marks
Explain how negative feedback control of blood glucose concentration returns it to normal after a carbohydrate-rich meal, and explain why a person with type 1 diabetes cannot do this.
Command word: Explain — how to answer itMark scheme — 7 creditworthy points
- Rise in blood glucose is detected by beta cells in the islets of Langerhans in the pancreas
- Beta cells secrete insulin into the blood
- Insulin binds to receptors on liver and muscle cell membranes
- More glucose transporters are moved into the membrane, so glucose uptake increases
- Insulin activates enzymes that convert glucose to glycogen (glycogenesis) and increases respiration of glucose
- Blood glucose falls, insulin secretion is reduced - negative feedback
- In type 1 diabetes beta cells are destroyed (autoimmune), so little or no insulin is secreted and glucose stays high / is lost in urine
Full-mark answer
The rise in blood glucose after the meal is detected by the beta cells in the islets of Langerhans in the pancreas, which secrete insulin into the blood. Insulin binds to receptors on the cell surface membranes of liver and muscle cells, causing more glucose transporter proteins to be inserted into the membrane so that glucose uptake increases. Insulin also activates enzymes that convert glucose to glycogen and increases the rate at which glucose is respired. Blood glucose concentration therefore falls back towards the set point, and as it does the beta cells reduce insulin secretion - this is negative feedback, because the response reverses the original change. In type 1 diabetes the beta cells have been destroyed by an autoimmune response, so little or no insulin is secreted; the liver and muscle cells do not take up or store glucose and blood glucose remains high, with glucose appearing in the urine.
Examiner insight: The negative feedback mark is only given for stating that the correction reduces the original stimulus. Also be precise about beta cells - 'the pancreas releases insulin' loses the detection mark.
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 2024 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 2024 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.