The document outlines key concepts in microbiology including: 1. Bacteria, viruses, fungi and protozoa are pathogens that can cause illness. Antibiotics work on bacteria but not viruses. 2. Phagocytic leukocytes defend the body by ingesting pathogens through chemotaxis, attachment, and using digestive enzymes in phagosomes to destroy the pathogens. 3. Antibodies and antigens are important concepts in immunity, with antibodies being produced in response to antigens to help fight infection. HIV attacks the immune system, leading to AIDS.

2. 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. 3
Assessment statements from: Online IB Biology Subject GuideCommand terms: http://i-biology.net/ibdpbio/command-terms/

6. Bacteria
• Prokaryotes (no real nucleus)
• Divide by binary fission
Can cause:
• Food poisoning (e.g. Salmonella)
• Ear and eye infections
• Cholera, diarrhea
http://en.wikipedia.org/wiki/File:Ericson_Type
_II_Conjunctivitis.JPG

7. The 1918 flu epidemic killed between 50 and 130 million
people. http://en.wikipedia.org/wiki/1918_flu_pandemic
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 quickly
Cause:
• Flu, HIV/AIDS, smallpox, measles, common cold, herpes, ebola

8. Fungi
• Eukaryotes, reproduce with spores
Cause:
• Athlete’s foot, mould, ringworm
• Allergic reactions and respiratory
problems
Image from:
http://en.wikipedia.org/wiki/Athlete's_foot

9. Protozoa
• Simple parasites
Cause:
• Malaria
• Leishmaniasis
• Toxoplasmosis
Leishmaniasis image from:
http://en.wikipedia.org/wiki/Leishmaniasis

16. Antibiotics are ineffective
against viruses!
http://www.youtube.com/watch?v=RedO6rLNQ2o
Over-use of antibiotics is accelerating the
evolution of more harmful bacteria. We are
running out of antibiotics that work and are
selecting 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:
http://www.wiley.com/college/pratt/0471393878/student/activities/bacterial_drug_resistance/index.html

18. Antibiotics are ineffective
against viruses!
Chlamydia trachomatis bacteria. Are you ready for the
end of antibiotics? Guardian: http://gu.com/p/2jxgj
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
write your own DBQ practice questions.
The scariest graph you’ll ever see. Read the article by Maryn McKenna:
http://www.wired.com/wiredscience/2011/02/not-many-antibiotics/

21. http://apchute.com/lymphatic/inflam.html

22. Phagocytic Leucocytes
“eating cell” “white blood cells”
Chemotaxis (movement in response to chemicals) attracts
the phagocytes to the area of invasion as response to:
• proteins produced by the pathogen
• phospholipids released by damaged cells
The phagocyte attaches 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 digestive enzymes –
deposit the enzymes into the phagosome.
The digestive 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

23. Phagocytic Leucocytes card sort game: order the images
& outline the processes
Images from: http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/animation__phagocytosis.html