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ch 19 - Chapter 19 The Diversity of Viruses Prokaryotes and...

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Chapter 19: The Diversity of Viruses, Prokaryotes, and Protists
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Viruses Characteristics of a virus: no cell membrane, no cytoplasm, no ribosomes – not a living thing Can only reproduce inside a host cell very small in size (0.05-0.2 micrometers) 2 major components constitute a virus : single or double stranded DNA or RNA Protein coat (may be surrounded by an envelope)
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Relative Sizes of Microorganisms
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Additional Viral Characteristics Viruses: cannot grow or reproduce on their own lack complex cellular orgainization have a specialized protein coat Viral genetic material hijacks host cell to produce new viral components Viral components assemble rapidly into new viruses and burst from host cell Come in a variety of shapes 0
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Viruses Are Host-Specific Each viral type is specialized to attack a specific type of host cell Bacteria are infected by bacteriophage viruses Bacteriophages are a virus that specifically attacks bacterial cells
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Treating Diseases With Viruses Bacteriophages can treat bacterial diseases Rise in bacterial antibiotic resistance makes standard drugs less effective Bacteriophages specifically target host bacteria Bacteriophages are harmless to human body cells Bacteriophages Bacterial cell
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Viruses of Multicellular Organisms Are Specific Cold viruses attack membranes of respiratory tract Measles viruses infect the skin Rabies viruses attack nerve cells
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Viruses of Multicellular Organisms Are Specific Some viruses linked to cancer (i.e. leukemia, liver cancer, cervical cancer) Herpes virus attacks mucous membranes of mouth and lips (causing cold sores) Other herpes virus type causes genital sores HIV virus attacks the white blood cell in humans, causing AIDS
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HIV virus
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Viral Infections Are Difficult to Treat Antibiotics are ineffective against viruses Antiviral drugs may also kill host cells Viruses hide within cells, are hard to detect Viruses have high mutation rates Mutations can create resistance to antiviral drugs Resistant viruses spread and multiply, rendering the drug ineffective
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Viruses as Biological Weapons Difficulty in treating viral infections makes viruses devastating weapons Limited smallpox stocks saved to develop future vaccine against unknown stocks Ebola hemorrhagic fever kills 90% of victims (no treatment or vaccine known)
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