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Option F: Microbes and Biotechnology (HL only) F.6 Microbes and Disease F.6.1 List 6 methods by which pathogens are transmitted and gain entry to the body 1. 2. 3. 4. 5. 6. Food Water Aerial Animal vectors Puncture wounds Sexual contact F.6.2 Distinguish between intracellular and extracellular bacterial infection using Chlamydia and Streptococcus as examples Intracellular Extracellular Example Chlamydia Streptococcus Location Lives inside cell Lives outside cells Toxins None Yes Damage to cells Indirect; long term problems Direct damage (invasin) Immune system Not targeted (hidden) Immediately targeted F.6.3 Distinguish between endotoxins and exotoxins F.6.4 Evaluate methods of controlling microbial growth by irradiation, pasteurization, antiseptics and disinfectants Irradiation: gamma rays/microwaves/UV rays used to destroy nucleic acids Pasteurization: heating to a specific temperature to ensure that pathogenic bacteria are destroyed (i.e. milk) Antiseptics: mild chemicals used to kill bacteria without damaging skin and mucous membranes (i.e. 50-80% ethanol) Disinfectants: Kill bacteria but no endospores; damaging to skin and mucous membranes (i.e. bleach, Lysol) F.6.5 Outline the mechanism of the action of antibiotics, including inhibition of synthesis of cell walls, proteins and nucleic acids 1. Cell wall synthesis inhibition: interferes with peptidoglycan/cell wall cross linkages (penicillin) 2. Protein synthesis inhibition: binds to 70S ribosomes (streptomycin) 3. Nucleic acid inhibition: inhibits synthesis of nucleic acids (Rifampicin) F.6.6 Outline the lytic life cycle of the influenza virus Put these in order • Virus uncoats in endosome • The virus is taken up into an endosome via endocytosis • The nucleocapsid recognises specific points on cell membrane where viral proteins have become inserted and buds off to release new virus particles • Viral RNA is transported to nucleus • Viral RNA is released into cytoplasm • Transcription of viral mRNA occurs • Some viral mRNA is transported back to cytoplasm where translation of viral proteins occur. Some serves as template for more RNA • Viral envelope proteins are packaged at Golgi apparatus and transported to cell membrane • The virus attaches to specific cell surface receptors on host cell • The ER makes viral envelope proteins in cytoplasm Put these in order • • • • • • • The virus attaches to specific cell surface receptors on host cell The virus is taken up into an endosome via endocytosis Virus uncoats in endosome Viral RNA is released into cytoplasm Viral RNA is transported to nucleus Transcription of viral mRNA occurs Some viral mRNA is transported back to cytoplasm where translation of viral proteins occur. Some serves as template for more RNA • The ER makes viral envelope proteins in cytoplasm • Viral envelope proteins are packaged at Golgi apparatus and transported to cell membrane • The nucleocapsid recognises specific points on cell membrane where viral proteins have become inserted and buds off to release new virus particles F.6.7 Define epidemiology • The study of the occurrence, distribution and control of disease in a population F.6.8 Discuss the origin and epidemiology of one example of a pandemic • • • • • • • • • Definition Name example Cause of occurrence Mode of transmission Symptoms Effect Health measures International factors TOK consideration/correlation and cause F.6.9 Describe the cause, transmission and effects of malaria, as an example of disease caused by a protozoan Cause: Plasmodium Transmission: Female Anopheles mosquito • Plasmodia reproduce in mosquito gut and egg sac ruptures to release sporozoites which travel to its salivary glands Effects: • Anaemia • Fever chills • Shivering • Headache • Pain in joints F.6.10 Discuss the prion hypothesis for the cause of spongiform encephalopathies Scrapie Bovine spongiform encephalopathy (BSE) Variant CreutzfeldtJackob disease (vCJD) F.6.10 Discuss the prion hypothesis for the cause of spongiform encephalopathies • • • • • • • • • • Prions are infective agents that are made of protein only It is believed that this is the cause for neurodegeneration It is believed that it causes BSE/CJD/scrapie The transmission of the disease did not fit any conventional theory Transmission can occur by eating infected foods Prions cause other normal proteins to fold abnormally Two forms: PrPsc (misfolded) and PrPc (wild type) PrPsc cause of disease PrPsc can cause PrPc to misfold PrPc found naturally in brain cell membranes but function is unknown