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Viruses and Bacteria
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What is a virus? DNA or RNA enclosed in a protein coat
A parasite of an organism Non-living: not made of cells, unable to reproduce, feed, do not die Human AIDS virus
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Virus Structure Protein coat (capsid) contains the DNA or RNA
It attaches to and tricks its host cell into letting it inside Once inside the viral DNA or RNA takes over
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How do Viruses Reproduce?
Lytic Infection Virus enters cell Host cell is directed to copy the viral DNA Cell bursts open releasing new viruses Examples: flu, cold, Lysogenic Infection Virus enters cell Virus attaches to host DNA Replication of host and viral DNA Cell does not burst right away Eventually becomes lytic Examples: HIV, retroviruses
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What are Bacteria? Simplest living things Single celled prokaryotes
No nucleus or other membrane-bound organelles Three basic shapes Can be arranged in clusters (staphylo-) or chains (strepto-)
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Bacteria Structure Cell wall made of peptidoglycan Cell membrane
Ribosomes Some have flagella to move through water Many do not move
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Some Bacteria are Dangerous
Diseases Cholera Tuberculosis Tetanus Salmonella food poisoning Botulism Staphylococcus infections of skin A soldier dying of tetanus (Painting by Sir Charles Bell)
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Most Bacteria are Helpful
Important uses of Bacteria Recycling nutrients (decomposers) Nitrogen fixers Making certain foods Cheese, sour cream, butter, vinegar
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Cheese facts… Cheese came into being in prehistoric times.
Must have resulted from the simple observation that milk left in a container ends up by coagulating, even more if it is hot. differentiated by: the type of milk - raw, skimmed or pasteurized by the animal - cow, goat, sheep, buffalo, horse or camel.
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