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7 Pages

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BIOL 1175

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Diseases Infectious Diseases  Epidemiology: study of diseases in populations  Infectious Diseases: diseases caused by pathogens o Bacteria o Viruses o Fungi o Protozoans o Helminths (worms) o Prions  Epidemic: More cases of the disease than expected in a certain area for a certain period  Outbreak: if the epidermic is confined to a local area  Pandemic: a global epidemic Infectious Agents  Bacterial and viruses are the most common infectious microbes (microscopic organisms)  Microbes that cause disease (note, not all do!) are called pathogens, but pathogens are not limited to microscopic organism or even living things (think parasitic worms and viruses)  When a microbe finds a tissue inside the body that will support its growth, it becomes infectious  If a microbe can spread from one organism to another, then it is contagious Bacteria  Bacteria o Prokaryotes  Lack a nucleus and other membrane-bound organelles o Cell wall of peptidoglycan o Three shapes  Sphere (coccus)  Rod (bacillus)  Spiral (spirilla) o Reproduction  Very rapid  Asexually by binary fission o Offensive mechanisms  Enzymes  Cause direct tissue damage  Toxins  Affect particular tissues  Example: C. botulinum toxin affects nervous tissue  Beneficial bacteria o Food production (yogurt, cheese) o Environment (decomposers, chemical cycles) o Genetic engineering o Normal inhabitants of the body that keep harmful organisms in check Antibiotics  Chemicals that inhibit the growth of microorganisms  Work by disrupting processes that are common to bacteria but not to human cells o Prevent synthesis of cell walls  Our cells lack cell walls o Block protein synthesis  Our ribosomes are slightly different How does antibiotic resistance develop? 1. Mutation and selection create drug resistant strains 2. conjugation transfers drug resistance from one strain to another What are viruses?  Small parasites that cannot reproduce by themselves  Infects a suitable cell and utilizes the host cell machinery and energy to produce more viruses  Viruses infect cells and the host range of most viruses is usually quite narrow,
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