AQA GCSE Combined Science: Trilogy Biology Paper 1 (Higher), 2019: Question 1

✅ Correct answer

B

This is the pulmonary artery, which carries deoxygenated blood from the heart to the lungs.

💡 Key knowledge

• The pulmonary artery is the only artery that carries deoxygenated blood.
• It leaves the right ventricle and goes to the lungs.
• Arteries usually carry blood away from the heart.

🧠 Exam technique

• Use the position of the vessel, not just the word “artery”.
• Look for the vessel leaving the right side of the heart towards the lungs.

❌ Common errors

• Choosing the aorta because it is also an artery.
• Thinking all arteries carry oxygenated blood.
• Mixing up the pulmonary artery and pulmonary vein.

✅ Correct answer

Right atrium

The pacemaker is the sinoatrial node (SAN), found in the right atrium.

💡 Key knowledge

• The SAN sets the natural resting heart rate.
• It sends electrical impulses that make the heart contract.
• It is in the wall of the right atrium.

🧠 Exam technique

• Learn the exact location: right atrium, not “top of the heart” or “near the centre”.
• In a one-mark question, write the precise structure named in the specification.

❌ Common errors

• Choosing the left atrium because it is also an upper chamber.
• Choosing the ventricles because they contract strongly.
• Writing “pacemaker” without saying where it is found.

✅ Correct answer

Foxgloves

Digitalis is a drug obtained from the foxglove plant.

💡 Key knowledge

• Some medicines are derived from plants.
• Digitalis is used to help slow the heart rate.

🧠 Exam technique

• Recall the specific plant name: foxglove.
• If you are unsure, eliminate obviously wrong options such as bacteria or mould.

❌ Common errors

• Choosing bacteria or mould because many medicines come from microorganisms.
• Confusing digitalis with other plant medicines from willow.

📐 Calculation steps

1. Use the equation: cardiac output = stroke volume × heart rate
2. Rearrange it to find stroke volume: stroke volume = cardiac output ÷ heart rate
3. Use the values from the taking beta blockers, at rest column:
   stroke volume = 2800 ÷ 52
4. Calculate: 2800 ÷ 52 = 53.846...
5. Round to 2 significant figures: 54 cm³

✅ Correct answer

X = 54 cm³

Any answer of 54 cm³ scores full marks.

🧠 Exam technique

• Always rearrange first before substituting numbers.
• Use the correct row and column from the table.
• Include the unit for full credit: cm³.
• Final answer should be to 2 significant figures.

❌ Common errors

• Using 2800 ÷ 88 or values from the wrong column.
• Multiplying instead of dividing.
• Writing 53.846 without rounding.
• Forgetting the unit cm³.

💡 Key knowledge to include

• During exercise, the body needs to transfer more energy.
• This means respiration increases.
• So more oxygen is needed and more carbon dioxide is produced.
• Beta blockers reduce heart rate.
• They also reduce stroke volume and therefore cardiac output.
• With lower cardiac output, less oxygen reaches muscle cells quickly enough.
• The breathing rate increases to try to bring in more oxygen and remove carbon dioxide, but it cannot fully compensate.

✅ A full-mark answer

During exercise the body needs to transfer more energy, so the rate of respiration increases and more oxygen is needed. Beta blockers reduce the increase in heart rate during exercise, and they also reduce stroke volume, so cardiac output is lower. This means less oxygen is delivered to the muscles and carbon dioxide is removed more slowly. The breathing rate increases to try to increase oxygen uptake, but this cannot fully make up for the reduced heart function, so the person gets out of breath.

🧠 Exam technique: how to reach Level 3

• Make sure your answer links exercise → more oxygen demand.
• Then explain beta blockers → lower heart rate/stroke volume/cardiac output.
• Finish with the effect on breathing and why this does not fully solve the problem.
• To get into the top band, your answer must be logical and connected, not just a list of facts.
• Use the data if helpful: heart rate during exercise is lower with beta blockers ( 88 vs 150 ).

❌ Common errors

• Only saying “beta blockers slow the heart” without explaining the consequence.
• Forgetting to mention exercise increases oxygen demand.
• Confusing breathing rate with heart rate.
• Saying the heart “stops” or oxygen “does not enter the lungs” — too vague or incorrect.
• Not linking lower cardiac output to less oxygen reaching muscles.

💡 Must-know facts

• Pulmonary artery = B
• Pacemaker cells = right atrium
• Digitalis comes from foxgloves
• cardiac output = stroke volume × heart rate
• Beta blockers lower heart rate and reduce cardiac output

🧠 Final exam tip

For 6-mark explanation questions, aim for a chain of reasoning:

exercise → more respiration → more oxygen needed → beta blockers reduce heart function → less oxygen delivered → breathing rate increases → still not enough.