CIE 11.5 Primary Defences against Pathogens (A-level)
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Questions and Answers

What role do goblet cells play in the primary defenses against pathogens?

  • They generate callose to block pathogens.
  • They secrete antimicrobial chemicals.
  • They secrete mucous to trap pathogens. (correct)
  • They produce gastric acid to destroy pathogens.
  • How do ciliated cells contribute to the primary defense in the respiratory tract?

  • They secrete callose to block pathogens.
  • They promote the growth of gut flora.
  • They produce gastric acid.
  • They sweep trapped pathogens out of the body. (correct)
  • Which of the following describes a primary defense in the human gut?

  • The presence of a waxy cuticle.
  • The secretions of goblet cells.
  • The acidic environment of the stomach. (correct)
  • The accumulation of callose in the intestines.
  • What is the function of the cuticle in plant defense?

    <p>It serves as a barrier to pathogen entry.</p> Signup and view all the answers

    What is callose and its role in plant defense?

    <p>A polysaccharide that blocks pathogen entry.</p> Signup and view all the answers

    Which of the following plants’ chemical defenses acts specifically against insect pests?

    <p>Saponins</p> Signup and view all the answers

    In plants, how does the presence of gut flora contribute to pathogen defense?

    <p>By preventing proliferation of harmful pathogens.</p> Signup and view all the answers

    What happens during expulsive reflexes in the body?

    <p>Pathogens are automatically expelled from the body.</p> Signup and view all the answers

    Which of the following best describes a secondary barrier to pathogen entry in plants?

    <p>Cell walls</p> Signup and view all the answers

    What is the primary disadvantage of the waxy cuticle for plants?

    <p>It prevents gas exchange.</p> Signup and view all the answers

    What is the primary role of the skin in the context of primary defenses against pathogens?

    <p>To act as a physical and chemical barrier</p> Signup and view all the answers

    Which of the following correctly describes the process of inflammation?

    <p>It is characterized by redness, heat, swelling, and pain</p> Signup and view all the answers

    What is the purpose of blood clotting during wound repair?

    <p>To prevent excessive blood loss and seal the wound</p> Signup and view all the answers

    What role do skin flora play in the body's primary defenses?

    <p>They help prevent colonization by harmful pathogens</p> Signup and view all the answers

    Which attribute is NOT characteristic of primary defenses?

    <p>They provide a tailored response to specific pathogens</p> Signup and view all the answers

    What happens to blood vessels during the inflammatory response?

    <p>They widen to allow more blood to the site of injury</p> Signup and view all the answers

    What is formed during blood clotting that aids in sealing a wound?

    <p>A network of fibrin along with platelets</p> Signup and view all the answers

    Which type of cells are primarily responsible for laying down collagen fibers during wound repair?

    <p>Fibroblasts</p> Signup and view all the answers

    What is one way the skin acts as a chemical barrier in the primary defenses against pathogens?

    <p>Producing sebum</p> Signup and view all the answers

    Which of the following accurately describes the effect of vasodilation during inflammation?

    <p>Increases the temperature and can lead to redness</p> Signup and view all the answers

    What is primarily responsible for the formation of the blood clot during wound repair?

    <p>Activation of platelets and protein fibers</p> Signup and view all the answers

    What is the main component that strengthens the skin barrier against pathogens?

    <p>Keratin found in the outer layer of skin</p> Signup and view all the answers

    Which process is essential for the repair of the skin barrier after injury?

    <p>Proliferation and migration of skin cells</p> Signup and view all the answers

    Study Notes

    Primary Defences

    • Defences that aim to stop pathogens entering the body
    • Can be physical or chemical
    • Non-specific, acts against any pathogen, not specific to one type

    Primary Defences In Animals

    • Skin
      • Physical barrier, dead cells, strengthened by keratin
      • Chemical barrier with antimicrobial fluid (sebum)
      • Skin flora - harmless microorganisms that prevent colonization by harmful pathogens
    • Inflammation
      • Protective response to tissue damage or foreign stimuli
      • Redness, heat, swelling, and pain
      • Swelling occurs due to vasodilation (blood vessels widen) and increased vascular permeability (blood vessels become leaky), bringing white blood cells to fight off pathogens
    • Wound Formation
      • Necessary to repair skin barrier after damage
      • Blood clotting - aggregation of platelets to plug wounds and prevent blood loss, creating a mesh of fibrin
      • Repair of the skin barrier - fibroblasts lay down collagen fibres, providing a foundation for new skin cells to attach and close the wound

    Mucous Membranes

    • Chemical defence in exposed areas (oral passages, nasal passages, eyes, ears)
    • Goblet cells secrete mucous that traps pathogens
    • Ciliated cells sweep trapped pathogens out
    • Expulsive reflexes (coughing, sneezing, vomiting) remove trapped organisms

    Gut

    • Chemical and flora primary defence
    • Stomach's acidity (gastric acid) destroys ingested pathogens
    • Colon has its own gut flora that prevents harmful pathogen proliferation

    Primary Defences in Plants

    • Physical
      • Waxy cuticle - barrier to pathogen entry, prevents water collection
      • Cell walls - secondary barrier to pathogen entry
      • Callose - polysaccharide secreted during stress, accumulates in cell walls and plasmodesmata to block pathogen entry and spread
    • Chemical
      • Antimicrobial chemicals - kill pathogens and prevent growth e.g. saponins
      • Phytoalexins - inhibit pathogen growth on plant surface
      • Insect poisons - deter insects and reduce viral transmission through insects

    Primary Defences

    • Primary defences aim to stop pathogens entering the body.
    • They can be physical or chemical.
    • Primary defences are non-specific.
    • They are barriers present to generally deter entry by any foreign organisms, and are not tailored responses to specific types of pathogens.

    Primary Defences in Animals

    • Skin: Forms a physical barrier made of dead cells, strengthened by keratin.
      • Secretes antimicrobial fluid (sebum).
      • Hosts skin flora: harmless microorganisms that prevent colonisation by harmful pathogens.
    • Inflammation: Protective response to pathogens or tissue damage.
      • Characterised by redness, heat, swelling and pain.
      • Swelling occurs as damaged cells release molecules causing vasodilation (blood vessels widen) and increased vascular permeability (blood vessels become more leaky).
      • This brings white blood cells and other immune components to the affected site quickly.
    • Wound formation: Repairs the skin barrier.
      • Blood clotting: plugs the wound, preventing excessive blood loss.
        • Platelets aggregate and form a mesh of fibres with fibrin.
      • Repair of the skin barrier: Fibroblasts lay down collagen fibres, providing a foundation for new skin cells to attach.
        • Skin cells proliferate and migrate towards the wound edge, closing the wound.
    • Mucous membranes: Chemical primary defence.
      • Found in oral passages, nasal passages, eyes and ears.
      • Goblet cells secrete mucus, trapping pathogens.
      • Ciliated cells sweep trapped pathogens back out.
      • Expulsive reflexes (coughing, sneezing, vomiting) remove trapped organisms.
    • Gut: Chemical primary defence and its own flora.
      • Stomach's acidic environment destroys ingested pathogens (due to gastric acid production).
      • Colon has its own microbiota (gut flora) that prevents harmful pathogen proliferation.

    Primary Defences in Plants

    • Physical defences:
      • Waxy cuticle: Acts as a barrier to pathogen entry.
        • Prevents water collection, reducing pathogen transmission between plants.
      • Cell walls: A secondary barrier to pathogen entry.
      • Callose: Secreted during stress (e.g. infection), blocking pathogen entry into and between cells.
        • Found at plasmodesmata, preventing pathogen spread from cell to cell.
    • Chemical Defences:
      • Antimicrobial and/or toxic chemicals: Kill pathogens or inhibit their growth.
        • Saponins: Destroy fungal cell membranes.
        • Phytoalexins: Inhibit pathogen growth on the plant surface.
      • Insect toxins: Reduce insect feeding, decreasing viral infection spread by insect vectors.

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    Description

    Explore the essential primary defenses that prevent pathogens from entering the body in animals. This quiz covers important concepts like skin barriers, inflammation responses, and wound healing. Test your knowledge of how these non-specific defenses function to protect against infections.

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