AQA GCSE Combined Science: Trilogy Biology Paper 1 (Foundation), June 2025: Question 5

✅ Correct Matches

• A → Vena cava [1 mark]
• B → Aorta [1 mark]

💡 Key Knowledge: Tracing the Flow

• Vessel A carries deoxygenated blood from the body into chamber F (Right Atrium) → it is the vena cava.
• Vessel B emerges from chamber D (Left Ventricle) and sends oxygenated blood out to the body → it is the aorta.
• Remember: On heart diagrams, the left side of the diagram is the body's right side!

❌ Common Errors

• Drawing multiple lines from a single letter box: the mark scheme explicitly warns "do not accept more than one line from a box on the left".
• Mixing up the pulmonary artery with the aorta (check which ventricle it leads from: Left = Aorta).

🧠 Exam Technique

Use a ruler to draw single, distinct lines. Look at the arrow directions: arrows pointing into the top chambers are veins; arrows pointing out of the bottom chambers are arteries.

✅ Correct Answer

Box F (Right Atrium) [1 mark]

💡 Key Knowledge: Cardiac Conduction

• The natural pacemaker is a cluster of specialised cells located in the wall of the right atrium (labelled F).
• These cells send regular electrical impulses that cause heart muscle to contract.
• If these fail, an artificial electronic pacemaker can be implanted.

❌ Common Errors

Choosing chamber C (the left atrium) or the ventricles (D / E). The natural pacemaker is strictly located in the right atrium.

❌ The #1 Biology Exam Trap

• NEVER say: "to produce / create / make energy". Energy cannot be created! Saying this completely cancels the mark. Always write "release energy".
• Do not say anaerobic respiration — the heart relies entirely on continuous aerobic respiration.
• Do not say "provides energy for respiration" — respiration is the process that releases energy, not consumes it.

🧠 Exam Technique: "Function → Mechanism → Purpose"

Whenever an exam asks why an active cell has many mitochondria, use the standard 3-step formula:

• Where/How: Site of aerobic respiration
• What: Releases energy
• Why: For muscle contraction / active transport

✅ Acceptable Symptoms (Any Two)

• Tiredness / fatigue [1 mark]
• Fast / increased breathing rate (rapid breathing) [1 mark]
• Fast / increased heart rate (or irregular heartbeat) [1 mark]
• Pale skin / blue skin (cyanosis) / cold skin [1 mark]
• Difficulty exercising [1 mark]
• Difficulty gaining weight / poor growth [1 mark]

💡 Biological Reason

A septal defect lets deoxygenated blood cross into the left ventricle and enter the aorta. Blood sent to the body carries less oxygen, so cells carry out less aerobic respiration, releasing less energy → resulting in fatigue and compensatory rapid breathing/heart rate.

❌ Common Trap: Vague Language

• "Shortness of breath" is explicitly marked as IGNORE in the mark scheme! You must state fast / increased breathing rate or difficulty breathing.
• Writing simply "pain" without context is too vague (the mark scheme accepts chest pain, but not unqualified pain).

✅ Acceptable Risks (Any Two)

• Infection (e.g. bacterial infection / MRSA) [1 mark]
• Heavy / internal bleeding [1 mark]
• Damaging blood vessels [1 mark]
• Damaging the heart wall / valves [1 mark]
• Blood clots / stroke / heart attack [1 mark]
• Risk from anaesthetic [1 mark]
• Rejection of the foreign mesh patch [1 mark]

❌ Examiner Pitfalls

• "Damage" on its own: The mark scheme states "ignore damage unqualified". You must specify what could be damaged (e.g. blood vessels or the heart).
• "Risk of disease": Too vague — say infection.