Communicable Diseases

    OCR
    GCSE

    Communicable diseases result from the invasion of pathogens—bacteria, viruses, protists, and fungi—transmitted via direct contact, vectors, or aerosol inhalation. The host defence relies on non-specific physical barriers and the specific immune response, where lymphocytes produce antibodies complementary to pathogen antigens. Control strategies encompass hygiene practices, isolation, and vaccination to establish herd immunity, while treatment distinguishes between symptom management and the use of antibiotics, which are ineffective against viral agents. Mastery requires understanding the interaction between pathogen replication and host immune mechanisms.

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    Objectives
    4
    Exam Tips
    4
    Pitfalls
    6
    Key Terms
    5
    Mark Points

    What You Need to Demonstrate

    Key skills and knowledge for this topic

    • Award 1 mark for stating that pathogens include bacteria, viruses, fungi, and protists
    • Credit responses that explain vaccination involves introducing dead or inactive pathogens to stimulate specific antibody production
    • Award 1 mark for explicitly stating antibiotics kill bacteria but are ineffective against viruses
    • Candidates must link the specific shape of the antigen to the complementary shape of the antibody produced by lymphocytes
    • For Level of Response questions on defense mechanisms, credit clear distinction between non-specific defenses (skin, mucus) and specific immune responses

    Example Examiner Feedback

    Real feedback patterns examiners use when marking

    • "You correctly identified the pathogen, but you need to be more precise about *how* it damages cells (e.g., toxins vs. cell lysis)"
    • "Avoid saying white blood cells 'fight' the disease; specify if they engulf the pathogen or produce antibodies"
    • "Great calculation of the inhibition zone area. To get full marks, explain what a larger zone implies about the antibiotic's effectiveness"
    • "You've confused antibiotics with antibodies here — remember antibiotics are drugs we take, antibodies are proteins we make"

    Marking Points

    Key points examiners look for in your answers

    • Award 1 mark for stating that pathogens include bacteria, viruses, fungi, and protists
    • Credit responses that explain vaccination involves introducing dead or inactive pathogens to stimulate specific antibody production
    • Award 1 mark for explicitly stating antibiotics kill bacteria but are ineffective against viruses
    • Candidates must link the specific shape of the antigen to the complementary shape of the antibody produced by lymphocytes
    • For Level of Response questions on defense mechanisms, credit clear distinction between non-specific defenses (skin, mucus) and specific immune responses

    Examiner Tips

    Expert advice for maximising your marks

    • 💡When describing the immune response, always refer to the 'complementary shape' of the antibody and antigen
    • 💡In questions about antibiotic resistance, ensure you state that random mutations occur *before* antibiotic exposure, not because of it
    • 💡For 6-mark questions on preventing disease spread, structure your answer by method: hygiene, isolation, and vaccination
    • 💡Memorize the specific vector for malaria (female Anopheles mosquito) as this is a frequent recall point

    Common Mistakes

    Pitfalls to avoid in your exam answers

    • Confusing 'antigens' (on the pathogen), 'antibodies' (produced by the body), and 'antibiotics' (medicines)
    • Stating that vaccines contain 'a small amount of the disease' rather than the pathogen or antigen
    • Believing antibiotics can treat viral infections like influenza or HIV
    • Describing white blood cells as 'eating' pathogens instead of using the correct term 'engulf' or 'phagocytosis'

    Key Terminology

    Essential terms to know

    Pathogen classification (Bacteria, Viruses, Fungi, Protists)
    Modes of transmission and physical/chemical barriers
    Specific immune response (Phagocytosis, Antibody/Antitoxin production)
    Vaccination principles and Herd Immunity
    Antibiotics, resistance, and the drug discovery pipeline
    Monoclonal antibodies (Higher Tier)

    Likely Command Words

    How questions on this topic are typically asked

    State
    Explain
    Calculate
    Suggest
    Compare
    Describe

    Practical Links

    Related required practicals

    • •{"code":"PAG 7","title":"Microbiological techniques","relevance":"Investigating the effectiveness of antimicrobials using agar plates and measuring inhibition zones"}

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