AQA GCSE Combined Science: Trilogy Biology Paper 1 (Higher), 2021: Question 5

✅ Correct answer

D

In the diagram, D is the pulmonary vein, which brings oxygenated blood from the lungs into the heart.

💡 Key knowledge

• The pulmonary vein carries the most oxygen-rich blood into the heart.
• It returns blood from the lungs to the left atrium.
• The pulmonary artery is different: it carries deoxygenated blood away from the heart to the lungs.

🧠 Exam technique

• Use the direction of blood flow, not just the shape of the vessel.
• Check whether the question says into the heart or out of the heart.

❌ Common errors

• Choosing the pulmonary artery because it sounds like a vessel linked to lungs.
• Thinking the vessel with the highest oxygen concentration must be an artery.

✅ Correct answer

C

C is the aorta, which carries blood from the left ventricle to the body at the highest pressure.

💡 Key knowledge

• Blood pressure is highest in the aorta because it leaves the heart directly after the left ventricle contracts.
• The left ventricle has the thickest muscle wall because it pumps blood all around the body.

🧠 Exam technique

• High pressure = vessel closest to the strongest pump on the left side of the heart.
• Remember: arteries carry blood away from the heart, but pressure is not the same thing as oxygen content.

❌ Common errors

• Picking the pulmonary artery because it is an artery.
• Mixing up pressure with oxygen concentration.

✅ Correct answer

right atrium → right ventricle → pulmonary artery

This is the route for deoxygenated blood from the heart to the lungs.

💡 Key knowledge

• Blood enters the right atrium first.
• It then goes into the right ventricle.
• The pulmonary artery takes it to the lungs.

🧠 Exam technique

• Learn the pathway as a chain, not as separate facts.
• For the lungs, remember: right side → lungs.

❌ Common errors

• Writing pulmonary vein instead of pulmonary artery.
• Starting on the left side of the heart when the question is about blood going to the lungs.

✅ What a full-mark answer needs

A strong answer must give advantages and disadvantages of both treatments, then make a clear judgement.

💡 Key knowledge

• Statins are drugs that reduce blood cholesterol.
• They help slow the build-up of fatty material in arteries.
• They are easy to take and do not require surgery.
• Possible disadvantages: side effects such as muscle pain, and they may need to be taken for life.
• Stents hold a blocked artery open.
• This increases blood flow to the heart muscle immediately.
• Possible disadvantages: operation risks such as infection, bleeding or a blood clot.

🧠 Exam technique

• To reach the top level, you need both sides of the comparison.
• Use comparative phrases: However , On the other hand , In contrast , Therefore .
• End with a judgement such as: Statins are better for long-term prevention, but stents are better for immediate relief.
• The examiner looks for a logical argument, not just a list.

❌ Common errors

• Only describing statins or only describing stents.
• Not saying which one is better for which situation.
• Forgetting that statins are a preventative treatment, while stents are a more direct treatment for a narrowed artery.

✅ Correct answer points

• The heart muscle cannot contract as effectively / powerfully.
• So less blood is pumped out to the body each beat.
• So less oxygen reaches body cells for aerobic respiration.
• Breathing rate increases to supply more oxygen or to repay oxygen debt / break down lactic acid.

💡 Key knowledge

• A heart attack damages heart muscle, so the pump becomes weaker.
• Less oxygen means cells may carry out more anaerobic respiration.
• Anaerobic respiration produces lactic acid, which contributes to fatigue and breathlessness.

🧠 Exam technique

• Use a chain of cause and effect: damage → weaker pumping → less oxygen delivery → breathlessness.
• For 4 marks, give at least 4 linked points.
• You can also mention oxygen debt and the need to remove lactic acid.

❌ Common errors

• Just writing “they have a bad heart” without explaining the effect on blood flow.
• Talking only about the lungs and ignoring the weakened heart pump.
• Confusing breathing rate with heart rate.

✅ Correct answer

Stem cells are undifferentiated, so they can differentiate into heart muscle cells.

💡 Key knowledge

• Stem cells are cells that have not yet specialised.
• They can develop into different types of cells.
• Here, they are needed because the damaged tissue needs new heart muscle cells.

🧠 Exam technique

• For 2 marks, include both: undifferentiated and can become heart muscle cells.
• Use the word therefore to show the link between the two ideas.

❌ Common errors

• Saying only “they are stem cells” without explaining why that helps.
• Writing “they can become any cell” without naming heart muscle cells.
• Using “specialised” instead of “undifferentiated”.

✅ Correct answers: any two

• Cells will not be rejected.
• No risk of damage to embryo.
• Adult can give consent.

💡 Key knowledge

• Using a person’s own cells means the body recognises them as “self”.
• Embryonic stem cells involve using an embryo, which raises ethical concerns.
• Consent is possible from an adult, but not from an embryo.

🧠 Exam technique

• Give two separate advantages.
• Write them clearly as two numbered points to avoid losing one mark.
• If you choose “not rejected”, make it clear that this is because the cells come from the person’s own body.

❌ Common errors

• Giving ethical opinions without linking them to the mark scheme.
• Saying “they are better” without saying why.
• Repeating the same idea twice, e.g. “not rejected” and “compatible” without extra detail.

💡 Heart and blood vessel facts

• Pulmonary vein carries oxygenated blood into the heart.
• Aorta carries blood at the highest pressure.
• Blood to the lungs travels: right atrium → right ventricle → pulmonary artery.

💡 Treatment facts

• Statins lower cholesterol and help prevent further artery narrowing.
• Stents open blocked arteries immediately.
• Top-band evaluation means comparing both, then judging which is better in which case.

💡 Stem cell facts

• Stem cells are undifferentiated.
• They can become specialised cells such as heart muscle cells.
• Using a person’s own cells avoids rejection.