Chapter 34 2.18.08

Chapter 34 2.18.08 - Chapter 34 1 Honors Biology Book Notes...

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Chapter 34 1 Honors Biology Book Notes Chapter 34 – Viruses 2/18/08 - Viruses o Not cells, not made up of cells, not considered organisms o Cannot copy themselves – take over host cell’s biosynthetic machinery and manufacture new generation of viruses with it o Characteristics DNA or RNA as hereditary material, single or double stranded No plasma membrane Viral transcription requires use of ATP and nucleotides of host cell Cannot carry out translation independently Virtually no metabolic capabilities Cannot replicate unless inside cell Typically 50-100 nanometers in diameter o Particles : also called agents, term given to viruses instead of scientific genus/species o Evolve and have genome o Bacteriophage : “bacteria-eater”, virus that infects bacteria o Reasons to study virus To minimize damage they cause To study their method of entering cell o Epidemic : describes disease that affects large number of people at same time o Virulent : tending to cause severe disease o AIDS [Aquired Immunodeficiency Syndrome]: caused by HIV [human immunodeficiency virus] HIV targets helper-T cells and macrophages, part of immune system Kills people indirectly by killing immune system cells, so bacteria and pathogens multiply in system unchecked and usually prove fatal Estimated 25 million already killed, some places in Africa have 1/3 population infected Focus of world-wide epidemic shifting from central/southern Africa to south/east Asia o Researchers who study viruses have 2 goals (1) Developing vaccines that allow hosts to fight off diseases if they become infected (2) Developing antiviral drugs that prevent virus from replicating efficiently inside host To do either, virus must first be isolated
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Chapter 34 2 Virus Causation Hypothesis : method of isolating viruses based on Koch’s postulates (1) Create filter which admits viruses but not cells (2) Expose healthy cells to filtrate (3) Virus isolated if healthy cells become infected o Analyzing Morphological Traits Use transmission electron microscopy Many viruses can be identified by shape alone – 2 main categories (1) Capsid : viruses can be enclosed by a shell of protein called capsid (2) Can be enclosed by capsid and membrane-like envelope Nonenveloped Viruses Extremely simple structure – consist of genetic material (genome) and possibly one or more enzymes inside capsid protein coat Enveloped Virus Genetic material inside capsid, which is surrounded by envelope Envelope consists of phospholipids bilayer with mixture of viral proteins and proteins derived from plasma membrane of host cell Vaccine : preparation that primes a host’s immune system to respond to a specific type of virus o Developing Vaccine Antibody : protein that binds with high specificity to particular site on one other particular compound Antigen : any molecule that elicits production of antibodies
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