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Biology_A-level_Cie

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  1. 1-1-the-microscope-in-cell-studies
    5 主题
  2. 1-2-cells-as-the-basic-units-of-living-organisms
    5 主题
  3. 2-1-testing-for-biological-molecules
    3 主题
  4. 2-2-carbohydrates-and-lipids
    8 主题
  5. 2-3-proteins
    6 主题
  6. 2-4-water
    2 主题
  7. 3-1-mode-of-action-of-enzymes
    5 主题
  8. 3-2-factors-that-affect-enzyme-action
    8 主题
  9. 4-1-fluid-mosaic-membranes
    4 主题
  10. 4-2-movement-into-and-out-of-cells
    12 主题
  11. 5-1-replication-and-division-of-nuclei-and-cells
    6 主题
  12. 5-2-chromosome-behaviour-in-mitosis
    2 主题
  13. 6-1-structure-of-nucleic-acids-and-replication-of-dna
    4 主题
  14. 6-2-protein-synthesis
    5 主题
  15. 7-1-structure-of-transport-tissues
    4 主题
  16. 7-2-transport-mechanisms
    7 主题
  17. 8-1-the-circulatory-system
    7 主题
  18. 8-2-transport-of-oxygen-and-carbon-dioxide
    5 主题
  19. 8-3-the-heart
    4 主题
  20. 9-1-the-gas-exchange-system
    6 主题
  21. 10-1-infectious-diseases
    3 主题
  22. 10-2-antibiotics
    3 主题
  23. 11-1-the-immune-system
    4 主题
  24. 11-2-antibodies-and-vaccination
    6 主题
  25. 12-1-energy
    5 主题
  26. 12-2-respiration
    11 主题
  27. 13-1-photosynthesis-as-an-energy-transfer-process
    8 主题
  28. 13-2-investigation-of-limiting-factors
    2 主题
  29. 14-1-homeostasis-in-mammals
    8 主题
  30. 14-2-homeostasis-in-plants
    3 主题
  31. 15-1-control-and-coordination-in-mammals
    12 主题
  32. 15-2-control-and-coordination-in-plants
    3 主题
  33. 16-1-passage-of-information-from-parents-to-offspring
    5 主题
  34. 16-2-the-roles-of-genes-in-determining-the-phenotype
    7 主题
  35. 16-3-gene-control
    3 主题
  36. 17-1-variation
    4 主题
  37. 17-2-natural-and-artificial-selection
    7 主题
  38. 17-3-evolution
    2 主题
  39. 18-1-classification
    5 主题
  40. 18-2-biodiversity
    7 主题
  41. 18-3-conservation
    6 主题
  42. 19-1-principles-of-genetic-technology
    11 主题
  43. 19-2-genetic-technology-applied-to-medicine
    4 主题
  44. 19-3-genetically-modified-organisms-in-agriculture
    2 主题
  45. 1-1-the-microscope-in-cell-studies
  46. 1-2-cells-as-the-basic-units-of-living-organisms
  47. 2-1-testing-for-biological-molecules
  48. 2-2-carbohydrates-and-lipids
  49. 2-3-proteins
  50. 2-4-water
  51. 3-1-mode-of-action-of-enzymes
  52. 3-2-factors-that-affect-enzyme-action
  53. 4-1-fluid-mosaic-membranes
  54. 4-2-movement-into-and-out-of-cells
  55. 5-1-replication-and-division-of-nuclei-and-cells
  56. 5-2-chromosome-behaviour-in-mitosis
  57. 6-1-structure-of-nucleic-acids-and-replication-of-dna
  58. 6-2-protein-synthesis
  59. 7-1-structure-of-transport-tissues
  60. 7-2-transport-mechanisms
  61. 8-1-the-circulatory-system
  62. 8-2-transport-of-oxygen-and-carbon-dioxide
  63. 8-3-the-heart
  64. 9-1-the-gas-exchange-system
  65. 10-1-infectious-diseases
  66. 10-2-antibiotics
  67. 11-1-the-immune-system
  68. 11-2-antibodies-and-vaccination
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Types of immunity

Active immunity

  • Active immunity is acquired when an antigen enters the body triggering a specific immune response (antibodies are produced)

  • Active immunity can be:

    • Naturally acquired through exposure to microbes

    • Artificially acquired through vaccinations

  • The body produces memory cells, along with plasma cells, in both types of active immunity

    • This gives the person long-term immunity

  • In active immunity, during the primary response to a pathogen (natural) or to a vaccination (artificial), the antibody concentration in the blood takes one to two weeks to increase.

  • If the body is invaded by the same pathogen again or by the pathogen that the person was vaccinated against then, during the secondary response, the antibody concentration in the blood:

    • Takes a much shorter period of time to increase

    • Is higher than after the vaccination or first infection

Graph showing primary and secondary antibody responses to antigens over 280 days, with sharp increase after second injection around day 120.
The primary and secondary response to the same antigen

Passive immunity

  • Passive immunity is acquired without an immune response

    • Antibodies are not produced by the infected person

  • As the person’s immune system has not been activated, there are no memory cells that can produce antibodies in a secondary response

    • If a person is reinfected they would need another infusion of antibodies

  • Depending on the disease a person is infected with (e.g., tetanus) they may not have time to actively acquire the immunity (there is no time for active immunity to occur)

  • Passive immunity occurs either artificially or naturally

    • Artificial passive immunity occurs when:

      • People are given an injection / transfusion of the antibodies—in the case of tetanus this is an antitoxin

      • The antibodies were collected from people whose immune system had been triggered by a vaccination to produce tetanus antibodies

    • Natural passive immunity occurs when:

      • Foetuses receive antibodies across the placenta from their mothers

      • Babies receive the initial breast milk from mothers (the colostrum) which delivers a certain type of antibody (IgA)

Feature

Active

Passive

Production of antibodies

Produced by the body

Not produced by the body

Time before antibodies appear in the blood

1-2 weeks

Immediate

Presence of memory cells

Yes

No

Induced naturally by:

Exposure to pathogen

Antibodies received from another organism (e.g. via the placenta during pregnancy)

Induced artificially by:

Vaccination

Antibodies are manufactured and injected / infused into the body (e.g. monoclonal antibodies given by blood transfusion)

Examiner Tips and Tricks

Active immunity is when the body produces the antibodies, whereas in passive immunity the body is given the antibodies.