OpenRevise

Exam questions · Biology · Defence Against Disease

Human Defence Systems

  • 7 exam questions
  • 20 marks
  • 8 quick checks
  1. 1 State [1 mark]

    Name the acid made in the stomach that kills pathogens.

    Show answerHide answer

    Model answer

    Hydrochloric acid.

    Mark scheme

    • Hydrochloric acid — 1 mark
  2. 2 Name [3 marks]

    Figure 1 shows the body's defences. Name the parts labelled A, B and C.

    A body with three parts marked A, B and C.
    Show answerHide answer

    Model answer

    A is the nose. B is the trachea. C is the stomach.

    Mark scheme

    • A: nose — 1 mark
    • B: trachea — 1 mark
    • C: stomach — 1 mark
  3. 3 Describe [2 marks]

    Describe how the nose helps to defend the body against pathogens.

    Show answerHide answer

    Model answer

    Hairs and mucus in the nose trap pathogens (and dust) in the air as it is breathed in, so they cannot reach the lungs.

    Mark scheme

    • Hairs / mucus — 1 mark
    • Trap pathogens — 1 mark
  4. 4 Explain [3 marks]

    Explain how the trachea and bronchi protect the lungs from pathogens.

    Show answerHide answer

    Model answer

    The cells lining the airways make mucus, which traps pathogens. Cilia on the surface move the mucus up the airways to the throat. The mucus is then swallowed, and the acid in the stomach kills the pathogens.

    Mark scheme

    • Mucus traps pathogens — 1 mark
    • Cilia move the mucus — 1 mark
    • Swallowed and killed by acid — 1 mark
  5. 5 Describe [3 marks]

    Describe three ways that white blood cells help to defend the body against pathogens.

    Show answerHide answer

    Model answer

    Phagocytes engulf and digest pathogens. Lymphocytes produce antibodies that stick to the antigens on pathogens. White blood cells also produce antitoxins, which neutralise toxins.

    Mark scheme

    • Phagocytosis — 1 mark
    • Antibody production — 1 mark
    • Antitoxin production — 1 mark
  6. 6 Explain [2 marks]

    Explain why an antibody that kills one type of bacterium does not kill another type.

    Show answerHide answer

    Model answer

    Antibodies are specific. The shape of an antibody fits only the antigen on one type of pathogen, so it cannot stick to a different one.

    Mark scheme

    • Antibodies are specific to one antigen — 1 mark
    • Shape does not fit a different pathogen's antigen — 1 mark
  7. 7 Describe [6 marks]

    Describe how the human body defends itself against pathogens.

    Show answerHide answer

    Model answer

    The skin is a barrier that most pathogens cannot get through, and platelets seal cuts with a scab. The nose traps pathogens in hairs and mucus. The trachea and bronchi make mucus that traps pathogens, and cilia move it to the throat to be swallowed. The stomach makes hydrochloric acid, which kills the pathogens. If pathogens do get in, white blood cells destroy them. Phagocytes engulf and digest them. Lymphocytes produce antibodies that stick to the antigens on the pathogen. Other white blood cells produce antitoxins to neutralise the toxins.

    Mark scheme

    • Skin barrier and scab — 1 mark
    • Nose hairs / mucus — 1 mark
    • Trachea and bronchi: mucus and cilia — 1 mark
    • Stomach acid kills pathogens — 1 mark
    • Phagocytosis — 1 mark
    • Antibodies and antitoxins — 1 mark

Quick check

  1. 1

    Which part of the body makes hydrochloric acid to kill pathogens?

    1. AThe nose
    2. BThe trachea
    3. CThe stomach
    4. DThe skin
    Show answerHide answer

    C: The stomach

    The stomach makes hydrochloric acid, which kills pathogens that are swallowed.

  2. 2

    What do cilia in the airways do?

    1. AMove mucus upwards
    2. BMake antibodies
    3. CEngulf bacteria
    4. DMake acid
    Show answerHide answer

    A: Move mucus upwards

    Cilia move mucus, with trapped pathogens, up the airways.

  3. 3

    What is phagocytosis?

    1. AMaking antibodies
    2. BEngulfing and digesting a pathogen
    3. CNeutralising a toxin
    4. DForming a scab
    Show answerHide answer

    B: Engulfing and digesting a pathogen

    In phagocytosis a white blood cell engulfs and digests a pathogen.

  4. 4

    What are antibodies?

    1. APoisons made by bacteria
    2. BParts of the skin
    3. CTypes of platelet
    4. DProteins that stick to specific antigens
    Show answerHide answer

    D: Proteins that stick to specific antigens

    Antibodies are proteins made by lymphocytes that stick to the antigens of a pathogen.

  5. 5

    Which cells make antibodies?

    1. ARed blood cells
    2. BPlatelets
    3. CLymphocytes
    4. DGuard cells
    Show answerHide answer

    C: Lymphocytes

    Lymphocytes, a type of white blood cell, produce antibodies.

  6. 6

    What do antitoxins do?

    1. ANeutralise toxins
    2. BEngulf bacteria
    3. CClot blood
    4. DCarry oxygen
    Show answerHide answer

    A: Neutralise toxins

    Antitoxins neutralise the toxins released by bacteria.

  7. 7

    Why is an antibody specific?

    1. AIt is made by a platelet
    2. BIts shape fits one type of antigen
    3. CIt is made in the stomach
    4. DIt is very large
    Show answerHide answer

    B: Its shape fits one type of antigen

    Its shape fits the antigen of only one type of pathogen.

  8. 8

    What forms at a cut to seal the wound?

    1. AA phagocyte
    2. BA cilium
    3. CAn antibody
    4. DA scab
    Show answerHide answer

    D: A scab

    Platelets help the blood clot, and the clot dries to form a scab.