Communicable Diseases, Disease Prevention and the Immune System (4.1.1): OCR A Level Biology Exam Questions by Topic

OCRBiodiversity, Evolution and DiseaseExam Questions
Written by Tom Whitburn

Communicable diseases and the immune system make up one of the biggest spec points in the OCR A course, and it is examined on every paper. Spec point 4.1.1 asks you to know the four types of pathogen and how they spread, how plants and animals defend themselves, how phagocytes and lymphocytes work, and the primary and secondary immune responses. You also need antibody structure, opsonins, agglutinins and anti-toxins, the types of immunity, autoimmune disease, vaccination programmes, sources of medicines and antibiotic resistance.

Students usually know the story of an immune response, but they lose marks on precise words. The examiners' reports keep flagging the same slips: saying the phagosome engulfs the pathogen, saying memory cells make antibodies, writing "active" without "artificial", saying "the body attacks itself" for autoimmune disease, and explaining natural selection when the question asks why resistance has become common.

Work through the eighteen questions below in order. They start with pathogens and the first lines of defence, move through the specific immune response and antibodies, and finish with vaccination, autoimmunity and medicines. If you'd like to go through questions like these with me each week, my OCR A masterclasses run on Wednesdays at 5.15pm for Year 12 and on Tuesdays at 6.30pm or Thursdays at 5.15pm for Year 13.

What you need from GCSE

Each question on this page assumes you're secure on these GCSE ideas. If any of them feels shaky, look it up before you start.

  • Pathogens are microorganisms that cause disease: bacteria, viruses, protists and fungi. They spread by direct contact, by water, through the air or by vectors.
  • The skin, mucus and cilia in the airways, and stomach acid stop many pathogens getting into the body.
  • White blood cells defend the body by phagocytosis, by producing antibodies and by producing antitoxins.
  • A vaccine contains a dead or inactive form of a pathogen. It makes white blood cells produce antibodies, so a later infection is destroyed quickly.
  • Antibiotics kill bacteria but not viruses, and bacteria can become resistant to them by natural selection.

Key terms

These words come up in the questions and mark schemes. Examiners expect you to use them exactly.

  • Antigen: a molecule, usually a protein on a cell surface, that the immune system recognises as self or non-self.
  • Antibody: a Y-shaped protein made by plasma cells, with two heavy and two light chains and a variable region that binds one specific antigen.
  • Phagosome and lysosome: the vesicle a phagocyte forms around an engulfed pathogen, and the organelle that fuses with it to release digestive enzymes.
  • Clonal selection and clonal expansion: activation of the lymphocyte with the matching receptor, then its rapid division by mitosis to make many identical cells.
  • Plasma cell: a B lymphocyte that has differentiated to make and release large amounts of one antibody.
  • Memory cell: a long-lived B or T lymphocyte that allows a faster, larger secondary response to the same antigen.
  • Opsonin, agglutinin, anti-toxin: antibodies that mark a pathogen for phagocytosis, clump pathogens together, or neutralise toxins.
  • Active and passive immunity: making your own antibodies and memory cells, or being given antibodies made by another organism.
  • Autoimmune disease: a disease in which the immune system attacks the body's own cells because it recognises them as non-self.
  • Herd immunity: protection of unvaccinated people because so many others are immune that the pathogen can't spread.

What these questions cover (OCR 4.1.1)

The questions test these learning outcomes from the OCR A Level Biology A specification (H420):

  • (a) the different types of pathogen that can cause communicable diseases in plants and animals (bacteria, viruses, protoctists and fungi)
  • (b) the means of transmission of animal and plant communicable pathogens (vectors, spores and living conditions)
  • (c) plant defences against pathogens (chemicals and callose)
  • (d) the primary non-specific defences against pathogens in animals (skin, clotting, inflammation, mucous membranes)
  • (e)(i) the structure and mode of action of phagocytes (neutrophils, APCs, phagosomes and lysosomes)
  • (e)(ii) examination and drawing of cells observed in blood smears (PAG1)
  • (f) the structure, different roles and modes of action of B and T lymphocytes in the specific immune response (clonal selection and expansion, T helper and T killer cells)
  • (g) the primary and secondary immune responses (memory cells)
  • (h) the structure and general functions of antibodies
  • (i) an outline of the action of opsonins, agglutinins and anti-toxins
  • (j) the differences between active and passive immunity, and between natural and artificial immunity
  • (k) autoimmune diseases (arthritis as an example)
  • (l) the principles of vaccination and the role of vaccination programmes in the prevention of epidemics
  • (m) possible sources of medicines (including personalised medicines)
  • (n) the benefits and risks of using antibiotics to manage bacterial infection

How to use this page

Write your answer on paper before you open the mark scheme. Allow about 1.2 minutes per mark: the 18 questions are worth 43 marks, so about 52 minutes in total. Then mark your answer strictly against the mark scheme and read the examiners' tip underneath it. If you'd rather print the questions, download the PDF pack.

Pathogens, transmission and plant defences

Question 1

AS Paper 2 · June 2024 · Q2(b) · 3 marks · Easy

Name the type of pathogen that causes influenza, malaria and black sigatoka.

Table with three diseases, influenza, malaria and black sigatoka in bananas, and an empty column for the type of pathogen.
Show the mark scheme Mark scheme: influenza is a virus, malaria a protoctist, black sigatoka a fungus. Only one answer per disease.

Tap an image to open it full size.

From the examiners' report: Learn the four pathogen types against the named diseases: black sigatoka is a fungus, but many wrote protoctist. Phonetic spellings of protoctist were accepted.

Question 2

A level Paper 3 · June 2019 · Q6(c) · 2 marks · Easy

Complete a passage on transmission by vectors and spores.

Passage with two gaps: animals that carry pathogens between hosts without symptoms are known as blank; P. infestans produces reproductive structures called blank carried on air currents.
Show the mark scheme Mark scheme: vectors; spores.

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From the examiners' report: Animals that carry a pathogen between hosts are vectors, and the potato blight pathogen spreads by spores on air currents. Most students got this; the slip was not recognising spores.

Question 3

A level Paper 3 · June 2025 · Q7(a)(ii) · 1 mark · Medium

Suggest why climate change might increase vector-borne disease.

Information from earlier in this question:

Earlier part of the same exam question, giving the information this part uses. Question asking why climate change might result in more cases of diseases caused by animal vector-transmitted pathogens.
Show the mark scheme Mark scheme: range of the vector increases; vector or pathogen populations increase or breed for more of the year; more standing water for breeding.

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From the examiners' report: Talk about the vector or pathogen: warmer conditions let vectors spread to new areas or breed for longer, so their numbers rise.

Question 4

A level Paper 3 · June 2025 · Q7(c) · 3 marks · Medium

Complete sentences about callose deposition in plants.

Sentences about a plant defence with three gaps: a polysaccharide called blank is deposited in channels called blank that pass through cell walls, and in gaps between sieve tube elements called blank.
Show the mark scheme Mark scheme: callose; plasmodesmata; sieve pores. Callus is ignored.

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From the examiners' report: Callose blocks the plasmodesmata and the sieve pores. The gaps between sieve tube elements are sieve pores; 'sieve plates' was the common wrong answer.

Non-specific defences and phagocytes

Question 5

A level Paper 2 · June 2023 · Q19(a) · 2 marks · Easy

Explain how mucous membranes make it harder for influenza virus to enter the body.

Question explaining that influenza spreads in exhaled droplets and asking how mucous membranes make it harder for the virus to enter the body.
Show the mark scheme Mark scheme: mucus traps the virus; cilia move the mucus away from the lungs.

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From the examiners' report: Say that the mucus traps the virus, not just 'the membrane traps it', then say the cilia move the mucus away. Cilia aren't microvilli.

Question 6

A level Paper 3 · June 2022 · Q2(a)(i) · 2 marks · Hard

Identify the white blood cells X and Y in a blood smear.

Fig. 2.1: light micrograph of a stained blood smear at ×800 with red blood cells, X a white blood cell with a large round nucleus filling most of the cell, Y a white blood cell with a lobed nucleus, and cells Z and W.
Show the mark scheme Mark scheme: X is a lymphocyte (T or B cell allowed), Y is a neutrophil (phagocyte allowed).

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From the examiners' report: A lymphocyte has a large round nucleus that almost fills the cell; a neutrophil has a lobed nucleus. Many students called X a macrophage or monocyte.

The specific immune response and antibodies

Question 7

AS Paper 1 · June 2019 · Q26(a) · 5 marks · Easy

Complete a passage on antigen presentation, T helper cells and B lymphocyte activation.

Passage about the specific immune response with five gaps and a word list: memory, plasma, killer T cell, antigens, antibodies, interleukins, phagocyte, meiosis, mitosis, hormones.
Show the mark scheme Mark scheme: antigens, interleukins, mitosis, plasma, antibodies.

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From the examiners' report: T helper cells release interleukins, not hormones, and it is plasma cells, not memory or killer T cells, that make antibodies. Keep antigens and antibodies apart.

Question 8

AS Paper 2 · June 2022 · Q4(b)(i) · 1 mark · Medium

Identify the type of immunity given by a flu vaccine.

Question stating that many people are given a flu vaccine each winter and asking for the type of immunity it gives.
Show the mark scheme Mark scheme: artificial active immunity.

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From the examiners' report: Give both words: artificial and active. Herd immunity is not a type of immunity in this sense.

Question 9

AS Paper 2 · June 2022 · Q4(b)(iii) · 2 marks · Hard

Outline the role of B memory cells in the secondary immune response.

Question asking students to outline the role of B memory cells in the secondary immune response.
Show the mark scheme Mark scheme: memory cells divide and differentiate into plasma cells, which produce antibodies rapidly; the antibodies bind to and disable the antigen or virus.

Tap an image to open it full size.

From the examiners' report: Memory cells don't make antibodies themselves. Say they divide quickly and become plasma cells, and the plasma cells release the antibodies.

Question 10

AS Paper 2 · June 2022 · Q4(c) · 3 marks · Medium

Outline the roles of phagosomes and lysosomes in phagocytosis.

Question asking students to outline the roles of phagosomes and lysosomes in phagocytosis.
Show the mark scheme Mark scheme: phagocyte engulfs the pathogen in a phagosome; lysosomes fuse with the phagosome; enzymes digest the pathogen. Lysozymes for enzymes not allowed.

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From the examiners' report: The phagocyte engulfs the pathogen; the phagosome is the vesicle it ends up in. Lysosomes contain enzymes; don't call them 'lysozymes'.

Question 11

AS Paper 2 · June 2018 · Q3(c)(ii) · 1 mark · Medium

Complete a diagram of an antibody by drawing and labelling the missing part.

Fig. 3.2: incomplete Y-shaped antibody showing only the two heavy chains joined by disulfide bridges.
Show the mark scheme Mark scheme: at least one light chain drawn on the outside of a heavy chain at the tip of an arm, 25 to 50% of its length, labelled light chain, variable region or antigen-binding site.

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From the examiners' report: Many students left this out. Draw a short light chain along the outside of each arm, starting at the tip, and label it light chain or variable region.

Question 12

A level Paper 3 · June 2022 · Q1(a) · 3 marks · Hard

Name the opsonin, agglutinin and anti-toxin shown in a diagram.

Fig. 1.1: R, an antibody binding a pathogen to a receptor on a white blood cell; S, antibodies linking several pathogens together; T, antibodies binding harmful molecules released by pathogens.
Show the mark scheme Mark scheme: R opsonin, S agglutinin, T anti-toxin.

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From the examiners' report: All three are antibodies, so name them as antibodies, not white blood cells. R, the one linking the pathogen to a phagocyte, is an opsonin and was the one most often missed.

Question 13

A level Paper 2 · June 2023 · Q19(b) · 5 marks · Medium

Match antigen presentation, clonal selection, clonal expansion and memory cells to parts of an antibody graph.

Fig. 19.1: antibody concentration against time with a small peak after the first exposure and a larger peak after the second; areas A to F mark stages, and a table lists five events to match.
Show the mark scheme Mark scheme: antigen presentation A; clonal expansion B and D; clonal selection A; high T helper activity B and D; highest number of memory cells E.

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From the examiners' report: Some events happen after both exposures, so they need two letters. Memory cells don't keep increasing to the end of the graph; their number falls over time.

Vaccination, autoimmunity and medicines

Question 14

AS Paper 2 · June 2023 · Q5(a)(iii) · 3 marks · Medium

Discuss a student's claim that the same flu vaccine is given every year.

Student statement that the flu vaccination programme gives the same flu vaccine to different age groups and medically vulnerable people every year, as it is for the same disease.
Show the mark scheme Mark scheme: different vaccines for different age groups; the vaccine changes each year because the virus mutates, so its antigens change and the immune system may not recognise it; it is correct that the vulnerable are offered it.

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From the examiners' report: Say it is the virus that mutates, so its antigens change and a new vaccine is needed. 'Medically vulnerable' means more at risk from the disease, not in need of a weaker vaccine.

Question 15

AS Paper 2 · June 2023 · Q5(a)(iv) · 2 marks · Medium

Explain how vaccination programmes help prevent epidemics.

Question asking how vaccination programmes can play a role in preventing epidemics.
Show the mark scheme Mark scheme: mass vaccination stops the pathogen spreading into the wider population; herd immunity; fewer further outbreaks or variants.

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From the examiners' report: Answer about the population, not one person: mass vaccination stops the pathogen spreading, as well as giving herd immunity.

Question 16

AS Paper 2 · June 2023 · Q5(b)(i) · 1 mark · Hard

Explain the meaning of autoimmune disease.

Question stating that rheumatoid arthritis is an autoimmune disease that causes pain in joints, and asking what autoimmune disease means.
Show the mark scheme Mark scheme: the immune system attacks the body's cells or tissues because it recognises them as foreign or non-self. 'Body attacks itself' is ignored.

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From the examiners' report: Name the immune system and say why it attacks: it recognises the body's own cells as non-self. An autoimmune disease is not a disease that attacks the immune system.

Question 17

A level Paper 2 · June 2023 · Q19(d) · 3 marks · Medium

Explain why many pathogenic bacteria are now resistant to antibiotics.

Question noting that antibiotics became widely available in the mid-20th century and asking why many pathogenic bacteria are now resistant to a range of antibiotics.
Show the mark scheme Mark scheme: widespread use or overprescribing; low doses or unfinished courses; natural selection with the antibiotic as the selective agent; sharing plasmids between bacteria.

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From the examiners' report: The question asks why resistance is now common, so start with overuse, low doses and unfinished courses before natural selection. Antibiotics don't cause the mutations.

Question 18

AS Paper 1 · June 2024 · Q24(d) · 1 mark · Medium

State what is meant by personalised medicine.

Question stating that personalised medicine may help with antibiotic resistance and asking what personalised medicine means.
Show the mark scheme Mark scheme: choosing medicines or treatments based on a person's genes, genome or genotype, or a treatment made for one patient matched to their infection.

Tap an image to open it full size.

From the examiners' report: Link the treatment to the person's genome or genotype. 'A drug specific to the individual' or 'based on their immune system' was too vague.

Where students lose marks (from OCR examiners' reports and mark schemes)

Each point below is followed by wording that gained marks.

  • Black sigatoka is a fungus: The most common slip in the pathogen table was writing protoctist for black sigatoka.

    ✔ Gains credit: "Influenza – virus", "malaria – protoctist", "black sigatoka – fungus".

  • It's the mucus that traps the virus: Many wrote that 'mucous membranes trap the pathogen' without mentioning mucus, so the first mark wasn't given.

    ✔ Gains credit: "Mucus traps pathogen / virus" and "cilia move mucus (away from lungs)".

  • Callose fills sieve pores, not sieve plates: Very few students named the gaps between sieve tube elements; 'sieve plates' was the usual wrong answer.

    ✔ Gains credit: "Callose", "plasmodesmata", "sieve pores".

  • Phagocytes engulf; phagosomes are the vesicle: Weaker answers said 'the phagosome engulfs the pathogen' and called the lysosome enzymes 'lysozymes', which wasn't allowed.

    ✔ Gains credit: "Phagocyte engulfs pathogen in a phagosome", "lysosomes combine with phagosome", "enzymes break down pathogen".

  • Plasma cells release the antibodies, not memory cells: Students wrote that 'memory cells remember the pathogen and produce antibodies'.

    ✔ Gains credit: Memory cells divide and differentiate into plasma cells; "plasma cells produce / release antibodies (rapidly)".

  • Two words for a flu jab: artificial active: Many gave only one of the two words, and the most common wrong answer was 'herd immunity'.

    ✔ Gains credit: "Artificial active (immunity)".

  • Autoimmune: the immune system sees self as non-self: 'The body attacks itself' was ignored, and some thought an autoimmune disease attacks the immune system.

    ✔ Gains credit: "Immune system attacks cells / tissues as it recognises them as foreign / non-self".

  • Resistance spread through overuse: Many spent the whole answer on natural selection and scored 1 mark, and some said antibiotics cause mutations.

    ✔ Gains credit: "Widespread use / overprescribing", "at low dose / unfinished course", "antibiotic is selective agent".

Download the questions

Download the PDF pack (18 questions, mark schemes at the end)

Keep practising

Questions, mark schemes and examiners' report extracts © OCR.

Tom Whitburn
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