AQA GCSE Combined Science: Trilogy Biology Paper 1 (Foundation), 2024: Question 3

✅ Correct answer

C

Mark point: 1 mark for the correct label.

💡 Key knowledge

• White blood cells are larger and have an irregular nucleus.
• Red blood cells are more numerous and look like pale discs.
• Platelets are tiny cell fragments, shown as small dots.

🧠 Exam technique

• Use the shape and size in the diagram, not just guesswork.
• White blood cells often stand out because they are fewer and bigger.

❌ Common errors

• Choosing a red blood cell because it is the most obvious structure.
• Mixing up platelets with white blood cells.

✅ Correct answer

Platelets

Mark point: 1 mark for naming platelets.

💡 Key knowledge

• Platelets help blood clot at a wound.
• Clotting helps prevent too much blood loss.

🧠 Exam technique

Write the exact biological term. “Blood cells” is too vague.

❌ Common errors

• Saying plasma, because plasma carries many substances but does not clot blood.
• Writing red blood cells.

✅ Correct answers

Any two from:

• oxygen
• hormones
• urea
• carbon dioxide
• water
• glucose
• amino acids
• fatty acids
• glycerol
• antibodies
• lactic acid
• minerals
• vitamins

Mark point: 1 mark for each correct substance, up to 2 marks.

💡 Key knowledge

Blood is a transport system. It carries useful substances to cells and waste substances away from cells.

Accept sugar for glucose.

Other correctly named substances can also be accepted, such as proteins.

🧠 Exam technique

• Give two different examples.
• Use clear science vocabulary: oxygen , glucose , carbon dioxide .

❌ Common errors

• Writing “food” or “nutrients” without naming a substance.
• Repeating the same idea in different words.

✅ Correct answer

Any one from:

• blood is under lower pressure
• easier to stop the bleeding
• easier to puncture the vein
• easier to access (vein / blood)
• less painful
• blood flows smoothly

Mark point: 1 clear reason for using a vein.

💡 Key knowledge

• Veins carry blood at lower pressure than arteries.
• Veins are often closer to the skin surface and have thinner walls.

🧠 Exam technique

The question asks for one reason only. A short, direct answer is enough.

❌ Common errors

• Talking about oxygenated vs deoxygenated blood — this is ignored.
• Giving a safety explanation instead of a biology reason.

✅ Correct answers

Advantage — any one from:

• improved quality of life
• lives are saved or deaths are reduced
• reduced anaemia
• restores blood levels after severe burns / blood loss

Disadvantage — any one from:

• risk of infection
• risk of rejection
• allergic reaction
• bruising

Mark point: 1 mark for one advantage and 1 mark for one disadvantage.

💡 Key knowledge

Blood transfusions can help replace blood quickly in emergencies, but they carry risks.

Blood type must match for safe transfusion; otherwise the wrong blood type may be given.

🧠 Exam technique

• For the advantage, link the transfusion to helping the patient.
• For the disadvantage, name a real medical risk.

❌ Common errors

• Writing a vague statement like “it is good” or “it is bad”.
• Repeating the same point for both advantage and disadvantage.

✅ Correct answers

Advantage — any one from:

• pleasure from helping others
• happiness from saving lives
• reveal potential health problems

Disadvantage — any one from:

• pain when donating
• risk of infection
• time spent while donating
• feeling unwell after donation
• bruising from the donation site
• reduced physical activity for the rest of the day
• possibility of rebleeding

Mark point: 1 mark for one advantage and 1 mark for one disadvantage.

💡 Key knowledge

• A donor may feel a “feel good” factor from helping others.
• Some donors may be told about possible health problems, including examples such as HIV.
• Common physical side effects include dizziness, nausea, sweating, trembling or fainting.

🧠 Exam technique

• Give one clear social/emotional benefit or health benefit.
• For the disadvantage, use a specific practical effect, not just “it is risky”.

❌ Common errors

• Using religious reasons — ignored by the mark scheme.
• Writing “pain” and “uncomfortable” as if they are two different marks.

💡 Core facts to memorise

• White blood cell = C in the diagram.
• Platelets cause clotting.
• Blood transports substances such as oxygen and glucose.
• Veins are used for donation because pressure is lower.
• Transfusion benefits patients, but there is a risk of infection or rejection.
• Donation can help others, but it may cause pain or bruising.

🧠 Top-mark strategy

• For 1-mark questions, one correct biology word is enough.
• For 2-mark questions, give two separate points.
• Use exact terms from GCSE biology: platelets , vein , infection , rejection .