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Carriers of Disease Microbes, Germs and Other Scary Things Bacteria • • • • Prokaryotic, monera 2 billion yrs 1st life on earth They change and adapt to the environment • No cell membrane or nucleus • Have cell wall • Many different structures Habitat • Extremes – Hot – Cold – Acidic – Alkaline • Everywhere on earth • Minority cause disease • Majority are essential to life on earth Diversity • 2 groups – Archeabacteria –halophytes, themoacidophiles, Methogens – poisoned by O2 – Eubacteria –all others • Pathogenic eubacteria cause about ½ of all human disease • Some destroy tissue – Exotoxins secrete substances that cause disease – Endotoxins – parts of the cells cause fever or shock Motility • ½ make direct movement • Flagella – most common form of movement, extension of plasma membrane • Spirochetes – spiral shaped that may have slimy chemicals excreted and a flagella • Taxis – have an attraction to chemical that may be beneficial or harmful Virus • Simplest form of life – Argument can be made that they may not be living • 1st discovered by Dr. Mayor in tobacco plants • Very small 20nm diameter • Consist of viral genes enclosed in capsid – a protein shell • There are multiple types of protein • Envelopes covering on capsid taken from the membrane of host • Phages – virus that infect bacteria RNA viruses • Single strand of nucleaic acid molecule involved in protein synthesis – Structure is specified by DNA • Retrovirus – most complicated reproduction – Can reverse DNA to RNA – New DNA integrates into host cell Evolutionary origins • Evolved after 1st cells from fragments of nucleacic acid • Developed capsid to promote infection • Viral genomes – plasmids – transposes DNA segments that move along genome • Virus replicate using the entire cell it infects Prion • Cause disease but aren’t bacteria, virus, parasite or fungi • They are protein and not alive • 1986 1st public awareness with onset of Mad-Cow Disease • Enter cell where they convert normal protein found within cell into prions like themselves • When normal cell is transformed into prion the amino acids are folded into alpha helical structures and relax into beta sheets • Prion then clog cells which decreases function or stops the cell from functioning all together • In brain tissue prion-bloated brain cells dies and release prion into tissue leaving holes in brain matter • Cause disease call spongiform encephalopathies Parasites • Single cell or multicell organism that feeds off host • Can survive only if host lives • Causes disease that are usually not fatal • Too many variety to list Fungi • Ecosystem would collapse without fungi – Decomposers – Recycles chemical elements in the environment • Positive uses for humans – Food – Cultures to produce antibiotics – Makes bread rise – Ferments to create beer and wine Characteristic • Eukaryote, multicellular • Heterotrophic • Excretes enzymes that break down molecules which it then absorbs\ • Can be parasitic or mutualistic Unique Lifestyles • Molds – grow as parasites on variety of substrates – Ex. – bread mold • Yeast – inhabit moist environments or liquids – Ex. - Candida Pathogenic Yeast in Humans • • • • • Athletes foot Ringworm Vaginal yeast infections Lung infections Nail infection