Defense against infections disease Ms. Fargo With some slides courtesy of Stephen Taylor

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. 6.3.5 Distinguish between antibodies and antigens. 6.3.6 Explain antibody production. 6.3.7 Outline the effects of HIV on the immune system. 6.3.8 Discuss the cause, transmission and social implications of AIDS.

Prokaryotes (no real nucleus) Divide by binary fission 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

Acellular (non-living?) 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 The 1918 flu epidemic killed between 50 and 130 million people. http://en.wikipedia.org/wiki/1918_flu_pandemic

Eukaryotes, reproduce with spores Cause: 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

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

Bactericidal vs. Bacteriostatic Bactericidal or fungicdal agents Kill microbes Bacteriostatic and fungistatic Stop further growth Don’t kill existing cells It is thought that because the growth of the pathogen is stopped, the body’s immune system will be able to kill it.

Antibiotics Can be selectively toxic by targeting such features as the Bacterial cell wall 70 S ribosomes This is the size of prokaryotic ribosomes Enzymes that are specific to bacteria. In this way, the human eukaryotic cells are unaffected.

Antibiotics are ineffective against viruses! 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. http://www.youtube.com/watch?v=RedO6rLNQ2o 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

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