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Defense Against Infectious Disease (Core)


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For the IB Biology course

Published in: Education, Health & Medicine

Defense Against Infectious Disease (Core)

  1. 1. Assessment Statements Obj. 6.3.1 Define pathogen. 1 6.3.2 Explain why antibiotics are effective against bacteria but not viruses. 3 6.3.3 Outline the role of skin and mucous membranes in defense against pathogens. 2 6.3.4 Outline how phagocytic leucocytes ingest pathogens in the blood and body tissues. 2 6.3.5 Distinguish between antibodies and antigens. 2 6.3.6 Explain antibody production. 3 6.3.7 Outline the effects of HIV on the immune system. 2 6.3.8 Discuss the cause, transmission and social implications of AIDS. 3Command terms: Assessment statements from: Online IB Biology Subject Guide
  2. 2. Bacteria • Prokaryotes (no real nucleus) • Divide by binary fissionCan cause: • Food poisoning (e.g. Salmonella) • Ear and eye infections • Cholera, diarrhea _II_Conjunctivitis.JPG
  3. 3. Viruses • Acellular (non-living?) • Need a ‘host’ cell to carry out functions of life, including reproduction • Can have DNA or RNA • Mutate, evolve and recombine quicklyCause: • Flu, HIV/AIDS, smallpox, measles, common cold, herpes, ebola The 1918 flu epidemic killed between 50 and 130 million people.
  4. 4. Fungi• Eukaryotes, reproduce with sporesCause:• Athlete’s foot, mould, ringworm• Allergic reactions and respiratory Image from: problems
  5. 5. Protozoa• Simple parasitesCause:• Malaria• Leishmaniasis• ToxoplasmosisLeishmaniasis image from:
  6. 6. Antibiotics are ineffectiveagainst viruses!Over-use of antibiotics is accelerating theevolution of more harmful bacteria. We arerunning out of antibiotics that work and areselecting for diseases such as MRSA. Antibiotics are designed to disrupt structures or metabolic pathways in bacteria and fungi: • cell walls and membranes • DNA synthesis (replication) • RNA polymerase • Translation These do not exist or are very different in viruses, so the antibiotic will have no effect.Bacterial drug resisance, from Wiley Essential Biochemistry. Find out more here:
  7. 7. Antibiotics are ineffectiveagainst viruses! Analyse the graph below. Over time, outline what has happened to: • The number of new approved antibiotics • The diversity of new approved antibiotics Suggest reasons for your answers. Use the graph to Chlamydia trachomatis bacteria. Are you ready for the write your own DBQ practice questions. end of antibiotics? Guardian: scariest graph you’ll ever see. Read the article by Maryn McKenna:
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  9. 9. Phagocytic Leucocytes “eating cell” “white blood cells”Chemotaxis (movement in response to chemicals) attractsthe phagocytes to the area of invasion as response to:• proteins produced by the pathogen• phospholipids released by damaged cellsThe phagocyte attaches to the pathogen’s cell surfaceproteins and then engulfs it. The fluid nature of theplasma membrane allows this to happen.A phagosome forms. This is a vesicle that contains thepathogen. Lysosomes – vesicles of digestive enzymes –deposit the enzymes into the phagosome.The digestive enzymes break down the pathogen and thewaste products are expelled from the cell by exocytosis. Review opportunity: • Plasma membranes and vesicles • Membrane fluidity and fusion • Endo- and exo-cytosis
  10. 10. Phagocytic Leucocytes card sort game: order the images & outline the processesImages from: