OCR GCSE Biology A: White blood cells, the immune system and vaccination (J247) – Practice Questions

These are original questions written for Marlbridge, for revision and practice on this content. They are not reproduced past-paper questions, and they do not replicate the exam’s exact structure, question count or mark tariffs – examination boards hold copyright in their own papers. Use these alongside the official past papers from your board or school.

These questions are aligned to the OCR GCSE (9-1) Gateway Science Biology A (J247) specification, Version 4.0 (August 2026), for first assessment in 2018. They cover statements B6.3j, B6.3k, B6.3l and B6.3o of module B6.3. None of these statements is in bold, so all are assessed in both Foundation and Higher Tier papers.

Learn the content first from the study guide and revision notes. Course pages: OCR GCSE Biology hub and printable checklist. All data in these questions are supplied for the exercise.

Questions

1. Platelets are not whole cells. State what platelets are and give one way they help to defend the body. [2]

2. Explain how a phagocyte is adapted to destroy pathogens. [3]

3. The trachea is lined with mucus-producing cells and ciliated cells. (a) Describe how these cells help to protect the lungs from pathogens. [3] (b) Explain why this is called a non-specific defence. [1]

4. A patient’s blood count is measured per mm³. Before infection the white blood cell count was 8000. During infection it was 14 400. After a treatment, the platelet count fell from 280 000 to 140 000. (a) Calculate the percentage increase in white blood cells. [2] (b) Calculate the percentage fall in platelets. [2]

5. A cut on a finger bleeds, then stops. Explain how the bleeding stops. [4]

6. A volunteer is given an injection of an antigen on day 0 and a second injection on day 28. The antibody concentration in the blood was measured (arbitrary units).

Day	0	7	14	21	28	31	35	42
Antibody	0	3	15	8	4	60	120	90

(a) State the day on which the antibody concentration peaked after the first injection. [1] (b) Calculate how many times higher the peak after the second injection is than after the first. [2] (c) Explain why the response to the second injection is faster and larger. [3]

7. (a) Explain how a vaccination against a disease protects a person from later infection. [4] (b) Explain why a measles vaccine does not protect against chickenpox. [1]

8. (a) A boy has a bacterial ear infection. Name the type of medicine a doctor would prescribe. [1] (b) A man has influenza, caused by a virus. Explain why the doctor does not prescribe an antibiotic. [2] (c) A nurse cleans a wound with iodine solution before covering it. Name this type of substance and state its purpose. [2]

9. A population of 5 000 000 bacteria is treated with an antibiotic that kills 99.8 % of them. (a) Calculate the number of bacteria that survive. [2] (b) Explain how the surviving bacteria could produce a population that is mostly resistant. [3]

10. Before a vaccination programme there were 12 400 cases of a disease in one year. Five years after it started there were 310 cases in one year. (a) Calculate the percentage decrease in cases. [2] (b) Suggest two reasons why cases did not fall to zero. [2] (c) Suggest why a booster dose may be recommended. [1]

11. A trial gave a new vaccine to 2000 children. 1920 were protected against the disease. 300 had a sore arm for one day. One child had a serious allergic reaction. Evaluate whether it is worthwhile to offer the vaccine to all children. [6]

Answers

1. Platelets are small fragments of cells (they have no nucleus) [1]. They help blood to clot at a wound, which seals it and stops pathogens entering [1]. [2] Examiner insight: Give the fragment idea and a named function separately; “they fight germs” is too vague to link to a clot.

2. It can change shape / is flexible, so it can squeeze out of capillaries and engulf pathogens [1]. Its membrane folds around the pathogen to engulf it into a vacuole (phagocytosis) [1]. It has many lysosomes with enzymes that digest the pathogen [1]. [3] Examiner insight: For adaptation questions, state the feature and what it allows; a list of features with no function leaves the explanation incomplete.

3. (a) Mucus traps pathogens and dust [1]. Cilia move (beat) in a sweeping action [1] and carry the mucus upwards to the throat so it is swallowed, and the acid in the stomach kills many microbes [1]. (b) It works against any type of pathogen, not one specific pathogen [1]. [4] Examiner insight: Name the structure and its action, such as “cilia sweep mucus upwards”; “keeps germs out” does not show how.

4. (a) 14 400 - 8000 = 6400 [1]; 6400 / 8000 x 100 = 80 % [1]. (b) 280 000 - 140 000 = 140 000, and 140 000 / 280 000 x 100 = 50 % [1] for the method and [1] for the answer. [4] Examiner insight: Divide by the starting value. Show the change and the division clearly, so that your method can be followed even if the final figure is wrong.

5. Platelets stick to the damaged area and release chemicals [1]. Soluble fibrinogen is converted into insoluble fibrin [1]. Fibrin forms a mesh that traps red blood cells to make a clot [1]. The clot dries to a scab, which seals the cut, stopping blood loss and pathogens getting in [1]. [4] Examiner insight: Name fibrinogen and fibrin the right way round; “the blood goes solid” is not enough for a four-mark explanation.

6. (a) Day 14 [1]. (b) 120 / 15 [1] = 8 times [1]. (c) Memory cells were made after the first injection [1]. They recognise the antigen at once and divide quickly [1]. More lymphocytes make antibodies sooner than in the first response, giving a faster, higher peak [1]. [6] Examiner insight: “Memory cells” is the expected idea. Quote figures when comparing the curves, for example time to peak (14 days against 7 days).

7. (a) The vaccine contains antigens from the pathogen in a safe form (dead, inactive or weakened, or parts of it) [1]. Lymphocytes with matching receptors divide and make antibodies [1]. Memory cells remain in the blood [1]. If the real pathogen infects later, memory cells give a rapid, large response and the person does not get ill [1]. (b) The antigens are different, so the antibodies and memory cells do not fit chickenpox [1]. [5] Examiner insight: A common slip is to say the vaccine contains antibodies. The vaccine supplies antigens and the person makes the antibodies.

8. (a) An antibiotic [1]. (b) Antibiotics act on bacteria and not on viruses [1], so they would not treat the infection (and would add to the risk of resistance) [1]. (c) An antiseptic [1], used to kill microorganisms on the skin / wound to prevent infection [1]. [5] Examiner insight: An answer that only says “antibiotics do not work” gains little. State that the cause is a virus and the antibiotic acts on bacteria.

9. (a) 100 - 99.8 = 0.2 % survive [1]; 0.2 / 100 x 5 000 000 = 10 000 [1]. (b) Some bacteria carry a mutation that makes them resistant [1]. The antibiotic kills the non-resistant bacteria but the resistant ones survive [1] and reproduce, passing on the resistance, so most of the new population is resistant [1]. [5] Examiner insight: Say that resistance was there by mutation before the antibiotic was used. “Bacteria adapt to the drug” suggests the individual changes, which loses the link to natural selection.

10. (a) 12 400 - 310 = 12 090 [1]; 12 090 / 12 400 x 100 = 97.5 % [1]. (b) Any two of: not everyone was vaccinated; the vaccine does not protect everyone; new people arrive who are not immune, for example visitors or newborns [1] [1]. (c) Boosters raise the number of memory cells and antibodies again, so the protection lasts [1]. [5] Examiner insight: Two separate reasons are needed for two marks. Repeating the same idea in different words gives only one reason.

11. Benefits: 1920 / 2000 x 100 = 96 % protected [1]. Protected children make memory cells and do not get the disease [1]. Risks: 300 / 2000 x 100 = 15 % had a short-lived sore arm, which is minor [1]. One child in 2000 had a serious reaction, which is rare [1]. Limits: 4 % (80 children) were not protected, so some risk remains [1]. Judgement: benefits outweigh risks, so the vaccine is worthwhile for most children, though children known to have allergies need medical advice [1]. [6] Examiner insight: Evaluate answers do best with figures from the data, both sides, and a final judgement that follows from them.

Where marks are usually lost

• Writing “fight” or “attack” for white blood cells without engulfing, digesting or antibodies.
• Describing platelets as cells, or leaving out fibrin when explaining clotting.
• Forgetting that mucus is swept to the throat and swallowed, not coughed out only.
• Saying a vaccine contains antibodies instead of antigens.
• Not mentioning memory cells when asked about a faster second response.
• Dividing by the new value instead of the original in percentage change questions.
• Saying antibiotics treat viral infections or that bacteria “learn” resistance.
• Giving only one side in an evaluation question.

Next steps

• Revise with the revision notes.
• Read the study guide.
• Visit the OCR GCSE Biology hub and tick off the checklist.
• Take one of the free 10-minute diagnostics.
• Book a free trial class.

Official syllabus

OCR GCSE (9-1) Gateway Science Biology A (J247) specification, Version 4.0 (August 2026), first assessment 2018, published by OCR. These questions cover statements B6.3j, B6.3k, B6.3l and B6.3o.