AQA GCSE Biology Biology Paper 1 (Foundation), June 2023: Question 7

✅ Correct Answers

• 07.1: A (Left Atrium) [1 mark]
• 07.2: C (Right Ventricle) [1 mark]
• 07.3: Right atrium [1 mark]

💡 Key Knowledge: The Heart Layout

• Anatomical Mirror: Remember the left side of the diagram is the patient's right, and the right side is the patient's left.
• Atrium = Entrance: Blood enters atria at the top; ventricles pump blood out at the bottom.
• Chamber Map:
  • D = Right atrium (receives deoxygenated blood via vena cava)
  • C = Right ventricle (pumps deoxygenated blood to lungs via pulmonary artery)
  • A = Left atrium (receives oxygenated blood from lungs via pulmonary vein)
  • B = Left ventricle (pumps oxygenated blood to body via aorta; note its much thicker muscular wall)
• Pacemaker: A group of specialised cells in the wall of the right atrium that sends electrical impulses.

🧠 Exam Technique

Trace the blood flow with your finger:

Body → Vena Cava → Right Atrium (D) → Right Ventricle (C) → Pulmonary Artery → Lungs → Pulmonary Vein → Left Atrium (A) → Left Ventricle (B) → Aorta → Body.

❌ Common Errors

• Mixing up left and right because of the mirrored anatomical perspective.
• Confusing the natural pacemaker location (right atrium) with the ventricle.

✅ Correct Answers (Choose any two)

• Artery has a thicker layer of muscle tissue.
• Artery has a thicker layer of elastic tissue (or simply thicker wall if neither muscle/elastic is credited).
• Artery has a narrower lumen (central channel).
• Artery does not contain valves (veins have valves to prevent backflow).

Note: Converse statements describing the vein are equally acceptable.

🧠 Exam Technique: Comparative Words

Always use comparative words (thicker, narrower, smaller) rather than absolute terms ("arteries have thick walls"). A vein also has muscle and elastic tissue—it just has less of it!

✅ 07.5: Describe the Trend [1 mark]

"As the percentage of coronary artery that is blocked increases, blood flow decreases."

Also accepted: negative correlation, inversely proportional, or the converse statement.

📐 07.6: Graph Construction [4 marks]

• 1 Scale (1 mark): Linear scale on y-axis (e.g. 0 to 100 with 20 per major grid division) occupying at least 50% of the grid height.
• 2 Plotting (2 marks): All 5 points plotted accurately to within ± ½ small square: (0, 100), (10, 64), (20, 42), (50, 8), (80, 2). [3–4 correct = 1 mark; all 5 = 2 marks].
• 3 Line of Best Fit (1 mark): A continuous, smooth curved line passing close to all points. Do NOT join dot-to-dot with straight lines!

✅ 07.7: Reading from Graph [1 mark]

Value read correctly from the candidate's drawn curve at x = 35%.

Standard acceptable range: 18 to 24 cm³/minute (tolerance of ± ½ small square from student's line).

🧠 Top Tip: Drawing Curve Lines of Best Fit

• Notice the steep drop at first (100 → 64 → 42) followed by a flattening out (8 → 2). This clearly requires a smooth curve, not a straight line.
• Rotate the exam paper so your wrist acts as a natural compass pivot to produce a single, non-feathered curve.

✅ Level 3 Indicative Points (Model Flow)

1. Reduced Blood Flow: Fatty material narrows the coronary artery, reducing blood flow to the heart muscle (cardiac tissue).
2. Deprivation of Reactants: Less oxygen and less glucose reach the heart muscle cells.
3. Reduced Aerobic Respiration: Less aerobic respiration can occur, releasing less energy / ATP for muscle contraction.
4. Anaerobic Respiration: Heart muscle respires anaerobically, resulting in a build-up of lactic acid.
5. Cardiac Symptoms: Lactic acid causes muscle fatigue and angina / chest pain (or ultimately a heart attack).
6. Systemic Body Effects: The heart pumps less blood around the body:
   • Less oxygen and glucose reach body tissues → causes tiredness / fatigue.
   • The breathing rate increases to compensate → causing breathlessness.

❌ Where Students Lose Marks

• Fatal Error 1: Thinking coronary arteries supply blood to the body rather than the heart muscle itself.
• Fatal Error 2: Saying "respiration produces energy" instead of "releases energy". Energy cannot be created!
• Stopping Too Early: Stopping at "heart gets less oxygen" without explaining the effect on cellular respiration and the resulting symptoms (tiredness, chest pain, breathlessness).

Option 1: Stent (Most Common)

• Treatment (1 mark): Insert a stent (a wire mesh tube).
• How it works (1 mark): It widens / holds the coronary artery open so blood flow to the heart muscle is maintained.

Option 2: Statins

• Treatment (1 mark): Prescribe statins (medication).
• How it works (1 mark): They reduce blood cholesterol levels, slowing down the rate of fatty deposit build-up.

Option 3: Bypass Surgery

• Treatment (1 mark): Coronary artery bypass surgery.
• How it works (1 mark): Uses a blood vessel from another part of the body to divert blood around the blocked section.

❌ Watch Out: Examiner Rejection

For a stent, writing "it unblocks the artery" is ignored by examiners! The mark scheme specifically requires stating that it keeps the artery open or widens the lumen.