Defense Against Infec.ous Disease
IB Bio 12
Assessment Statements Obj.
6.3.1 Define pathogen. 1
6.3.2 Explain why an.bio.cs are effec.ve 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 phagocy.c leucocytes ingest pathogens in the blood and body .ssues. 2
6.3.5 Dis6nguish between an#bodies and an#gens. 2
6.3.6 Explain an.body produc.on. 3
6.3.7 Outline the effects of HIV on the immune system. 2
6.3.8 Discuss the cause, transmission and social implica.ons of AIDS. 3
Assessment statements from: Online IB Biology Subject Guide Command terms: hPp://i-‐biology.net/ibdpbio/command-‐terms/
Bacteria • Prokaryotes (no real nucleus) • Divide by binary fission
Can cause: • Food poisoning (e.g. Salmonella) • Ear and eye infec.ons • Cholera, diarrhea hPp://en.wikipedia.org/wiki/
File:Ericson_Type_II_Conjunc.vi.s.JPG
The 1918 flu epidemic killed between 50 and 130 million people. hPp://en.wikipedia.org/wiki/1918_flu_pandemic
Viruses • Acellular (non-‐living?) • Need a ‘host’ cell to carry out func.ons of life, including reproduc.on • Can have DNA or RNA • Mutate, evolve and recombine quickly
Cause: • Flu, HIV/AIDS, smallpox, measles, common cold, herpes, ebola
Fungi • Eukaryotes, reproduce with spores Cause: • Athlete’s foot, mould, ringworm • Allergic reac.ons and respiratory problems
Image from: hPp://en.wikipedia.org/wiki/Athlete's_foot
Protozoa • Simple parasites Cause: • Malaria • Leishmaniasis • Toxoplasmosis
Leishmaniasis image from: hPp://en.wikipedia.org/wiki/Leishmaniasis
Life Cycle of Leishmania
3 Main Lines of Defense
1) Physical barriers – Skin, mucous membranes
2) Non-‐specific immune system – Phagocy.c leukocytes
3) An.gen-‐specific immune system – Lymphocytes (e.g. B-‐cells, T-‐cells, Killer cells)
hPp://apchute.com/lympha.c/inflam.html
Phagocy.c Leucocytes “ea.ng cell” “white blood cells”
Chemotaxis (movement in response to chemicals) aPracts the phagocytes to the area of invasion as response to: • proteins produced by the pathogen • phospholipids released by damaged cells The phagocyte aPaches to the pathogen’s cell surface proteins and then engulfs it. The fluid nature of the plasma membrane allows this to happen. A phagosome forms. This is a vesicle that contains the pathogen. Lysosomes – vesicles of diges.ve enzymes – deposit the enzymes into the phagosome. The diges.ve enzymes break down the pathogen and the waste products are expelled from the cell by exocytosis.
Review opportunity: • Plasma membranes and vesicles • Membrane fluidity and fusion • Endo-‐ and exo-‐cytosis
Phagocy.c Leucocytes card sort game: order the images & outline the processes
Images from: hPp://highered.mcgraw-‐hill.com/sites/0072495855/student_view0/chapter2/anima.on__phagocytosis.html