+ Chapter 7: Infection and disease 1 EL: To explore what a disease is and what causes them + Study design – key knowledge detecting ‘self’ and ‘non-self’ molecules: antigens and membrane receptors – pathogens: non-cellular agents, cellular agents; controls; physical and chemical barriers to infection in plants and animals; immune response – structure and overall function of the lymphatic system – non-specific: inflammatory response; phagocytosis; blood clotting – specific immune response: T-cell lymphocytes and cell-mediated response; B-cell lymphocytes and humoral response, antigens and antibodies; memory cells; disorders of the immune response: autoimmunity; hypersensitivity, allergens and allergic responses; acquired immunity: natural, artificial including vaccines and antibody serums. Chapter 7: Pre-test Question What is a disease? What is a pathogen What is a cellular agent? What is a non-cellular agent? Start of unit End of unit + Disease Any condition that interferes with how an organism or any part of it functions Can be acquired through: Genetic causes – inherited from parents Pathogens and parasites + Pathogens disease causing organism or agent (frequently but NOT always a MO) Non-cellular Prion virus Cellular pathogens pathogens bacteria fungi protozoa exo- and endo-parasites + + Nature of Disease Intensity of pathogenic effect: VIRULENCE Due to special characteristics of the pathogenic organism, such as ability to produce toxins Individuals level of susceptibility to pathogen: RESISTANCE Varies with age, state of health, immunity Some pathogens are able to survive outside the host, others are not Time between infection and symptoms: INCUBATION PERIOD Depends on pathogen achieving sufficient numbers, reaching target tissue, toxin accumulation etc + Nature of Disease: Transmission Infective agents can be transmitted from one host to another by: Direct contact Droplets in air breathed or sneezed by host Sexual contact (e.g. STIs) Contaminated food or water A carrying vector (e.g. rats carrying fleas) An injecting vector (e.g. mosquitoes carrying malaria parasites) Injection with infected needles and syringes + Non cellular pathogens: Viruses A virus is a non-cellular agent composed of a protein coat (capsid) and nucleic acid (RNA OR DNA) Rely on living cells to function and replicate: Not able to respire OBLIGATE intracellular parasites Often integrated into host chromosomes and replicated during cell division Highly specific to host cell or organism it infects (e.g. adenovirus specific to lung cells -> common cold) All organisms on Earth are susceptible to virus infection (e.g. bacteriophages) http://www.youtube.com/watch?v=Rpj0emEGShQ Chicken pox + Shingles + Rubella or German measles + Mumps + Cold sore + Warts + Verruca + Polio + Small pox – a killer + Non cellular pathogens: Prions Proteinaceaous GENOME infectious particles: NO Deviant versions of a normal cell surface protein that are transmissable Disease caused by accumulation of abnormal protease-resistant protein Diseases include BSE (or mad cow), CJD, Kuru + Cellular pathogens: Bacteria Prokaryotic Contain organisms lacking organelles circular DNA molecule Can be classified according to metabolic characteristics and/or shape Round Rod-shaped Spiral + Cellular pathogens: Bacteria Cell wall contains PEPTIDOGLYCAN and is chemically and morphologically complex Can have flagellum, capsules or spores Reproduce rapidly by binary fission in favourable conditions http://www.youtube.com/watch?v=gE wzDydciWc&NR=1 + Eye infection + Leprosy + Tetanus + Plant blight + NOB Activity 7.1 & 7.2 One group will set up activity 7.1 pg 58-59 (procedure 1-5) One group will set up activity 7.2 part A pg 61-62 (procedure 1-8) One group will set up activity 7.2 part B pg 63 (procedure 1-6) We will make observations next lesson + Homework – Chapter 7 Quick check qu 1-25 Biochallenge Chapter 1 Review qu 2 + Reflection What did you learn about infection and disease today? What was the most disgusting disease today? + Chapter 7: Infection and disease 2 EL: To examine our bacteria investigations + Activity 7.1 & 7.2 Everyone will complete: Activity 7.1 pg 59, procedure 6-8, qu 1-7 Activity 7.2 part A pg 63, procedure 9, qu 1- 8 Activity 10-15 7.2 part B pg 63, procedure 7, qu + Homework – chapter 7 Quick check qu 26-30 Biochallenge Chapter qu 2 review qu 4, 5, 6, 8 + Reflection Were you surprised by the results of any of the experiments and why? + Chapter 7: Infection and disease 3 EL: To further explore the causes of disease + Expected learning To further explore the causes of disease + Cellular pathogens: Fungi Eukaryotic heterotrophs break down organic matter by secreting enzymes and other chemicals These chemicals are the main cause of the disease Primarily moisture terrestrial, but need Reproduce Cell using spores wall made of chitin Filamentous moulds and unicellular yeasts + Athletes foot + Oral Thrush + Frogs – chytrid fungus + Cellular pathogens: Protists Unicellular Very eukaryotic organisms diverse Usually motile (i.e. flagella, cilia) Heterotrophic Reproduce May sexually and asexually have specialist life cycle involving different hosts + Protist Life Cycle http://www.youtube.com/watch?v=Q_nCHDry0s8 + Endoparasites: worms Flat and round worms may be parasitic, but aren’t necessarily pathogenic Pathogenic worms include tapeworms, roundworms + Endoparasites: worms + Ectoparasites: arthropods Generally parasitic, but aren’t necessarily pathogenic Pathogenic arthropods include head lice and body lice + Nelson Activity 5.2 Complete activity 5.2 and hand in + Reflection Why do you think parasites have evolved such a complex life cycle?