bio ch 19
Terms
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- Virus
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Latin="poison"
-obligate parasites, infectious agents
-a nonliving, noncellular particle consisting of a protein coat(specialized to help virus enter host cell) & nucleic acids(DNA,RNA-circular or linear)
-replicates inside a host cell
-no cytoplasm, no energy source, no ribosomes, no membranes - therefore can't make protein
-very small-0.05 to 0.2
-most can only be seen w/ electron microscope - Discovery of Viruses
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-scientists of 19th C noted that bacterial filters could not preven Hoof & mouth disease of Tobacco mosaic-so diseases were caused by something smaller
-1930s-electron microscope invented
1935-Stanley discovered that Tobacco mosaic virus, (TMV) was made of protein & RNA - Viral Replication
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1.virus enters host cell(accomplised in diff. ways)~englufed by endocytosis or viral surface proteins may bind to receptors on cells*once virus in cell-releases genetic material
2.virus uses cell's organelles & enzymes to replicate viral genetic material
3.viral genetic material is transcribed
4.viral mRNA uses host cell's cytoplasm & organelles to make viral proteins
5.new virus particles are assembled they consist of:genetic material,enzymes,surrounded by protein coat
6.virus particles are released from cell by budding/burst the cell - Lysogentic cycle
- takes longer, viral DNA or RNA gets passed on to new cells as host cell divides
- Latent infection
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virus may be present in our cells for a long time, not doing anything (dormant)
Then it may become active when triggered by some environmental factor (ex. stress, UV rays, illness)-Herpes simplex I (cold sores) - Viral Structure
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core: (inside) contains hereditary material(DNA or RNA), also contains reverse transcriptase to help copy viral DNA
protein coat:surrounds the nucleic acids
envelope:an outer layer formed from host cell's plasma membrane(lipid bilayer), it may contain "spikes" of glcoprotein - Host-specific viruses
- they can attack: plants(must get through cell wall) or animals(viruses are very specific to the type of tissue they attack)
- Examples of Host-specific viruses
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Herpes type I-mucus membrane of lips
Herpes type II-genital area
HIV-T cells
Influenza-epithials in respiratory system
Measles-skin
Rabies-nerve cells
Bacteria- bacteriophages -viruses that attack bacteria - Vectors
- some viruses are used to transfer genes from cells of on to cells of another species
- Examples of initiators of cancer
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Hepatitis B Virus(HBV)-liver cancer
Human T-cell Lymphotropic/Leukemia virus(HTLV)-can cause leukemia-abnormal or immature WBCs/Lymphoma-cancer of lymph
Human Papillomavirus(HPV)-assoicated w/cervical & penile cancer
Cytomegalovirus(CMV)-initiator of Kaposi's sarcoma
Epstein Barr virus(EBV)-associated w/ mononucleosis can cause cancer of the nose & throat - Examples of viruses classified as Transmitters of Sexual Diseases
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Human Immunodecifiency virus(HIV)-causes AIDS
Herpes Simplex Type 2(HSV2)-genital herpes-lesions
HPV-genital warts - Other viral diseases
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Smallpox
Ebola
West Nile virus
Polio - Viral Classification
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Type of host infected-plant, animal, bacterial
Morphology-shape & structure of virus
Nucleic acid-DNA or RNA
Method of replication-lytic of lysogenic(dormant) - Viral infections are difficult to treat because...
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-viruses are inside the body's cells-immune system can't "see" it
-some viruses mutate rapidly, so they evolve quickly and become resistant to antiviral drugs - Medications for viruses
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Acyclovir-for Herpes
Protease inhibitors-slows development of AIDS - Viroiods
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-circular strands of RNA particles with no protein coat
-enter host cell, make more viroids
-attack plants - Prions
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-mutated forms of protein particles that act as infections agents(transmitted in brain tissue)
-folded proteins, can be inherited-can't deactivate by heat
ex. Crutzfeldt-Jakob disease(vCJD)-destroy brain tissue
Bovine Spongiform Encephalitis(BSE)-mad cow disease
Chronic Wasting Disease(CWD)-deer, elk
*brain tissue gets spongey, holes
*can be passed on by eating infected animal parts - Archaea
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-prokaryotes, live in extreme conditions(hot, cold, acidic, salty)
-still being discovered and classified
-some are very old (ancient) - Bacteria
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-prokaryotes-single-celled, no nucleus or mitochondria
-0.2 to 10 micrometers
-cell walls contain peptidoglycan(sugar+a.a.)
-primitive, many types - Bacteria are classified by:
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-shape
-pigment
-nutrient requirements
-method of locomotion
-colony growth patterns
-Gram Staining characteristics - Classificatino of bacteria is changing rapidly because...
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-due to discovery of new organisms
-due to analysis of DNA and RNA
-new kingdoms being formed - Bacterial Shapes
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rod-like - - bacillus
spherical - - coccus
corkscrew-shaped - - sprillum - Bacterial Locomotion
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-accomplished by flagella:a hair-like extension through the plasma membrane
-arrangement may be:single, paired, tufted
-flagella move by rotating:wheel and axle
-flagella help bacteria: to get near food source and to move away from unfavorable environment - Biofilms
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-communities of sticky slime-secreting colonies of bacteria (one or more species)
-slime may be made of protein or polysaccharide (sugar)
-biofilms protect bacteria on inside layers from harsh chemicals-bleach, antibiotics
Ex. Dental plaque, inside of catheter tubes, on contact lenses, inside of pipes, flower vases - endospore
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-a protective structure formed by some rod-shaped bacteria
-contains genetic material and enzymes in a thick coat
-protects against harsh conditions(dryness, temperature)
-can survive for long periods of time
ex. anthrax and clostridium botulinum - Anthrax
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-bacterial endospores - Bacillus anthracis)
-spores are spread around easily-inhaled
-Anthrax vaccine (6 month innoculation)
-Inhalation anthrax=difficult to treat
-Cutaneous anthrax=topical antibiotic - Bacterial Reproduction: Asexual
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Binary fission-simple cell division producing two genetically identical cells
-can occure every 20 minutes
-many mutations due to bacteria evolving quickly - Bacterial Reproduction: Sexual
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Conjugation-involves two bacterial cells (may be diff. species)
-produces new genetic comninations-better variety
-membrances of 2 bacteria fuse, forming a bridge called pilus
-Plasmid DNA is transferred from one bacterium to the other through pilus
-DNA is then replicated - Bacterial Habitats
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Bacteria can survive in many extreme habitats-near boiling H20 (seavents), volcanoes, glaciers, high salinity, acidic, alkaline
How do they survive? Their enzymes are tightly folded nad bery rigid so they are not denatured by heat, acid - Methanogens
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rod-shaped, anaerobic, produce methane(CH4)
-live in marshes, bottom of lakes - Halphiles
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-require high concentrations of salt
-Great Salt Lake, Utah - Thermoacidophiles
- -live and grow in hot(100 C), acidic (pH=1) environments
- Bacterial Metabolism
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-some are anaerobic/some are aerobic
-some are able to metabolize (methane, H, S, Fe, NH3) - cyanobacteria
- blue/green bacteria that get energy through photosynthesis
- Useful bacteria
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-bacteria in our intestinal tract-help to digest food
-bacteria digest celluloes in digestive tract of many plant-eaters-rabbits
-bacteria ferment lactose to form-cheese & yogurt (Lactobacillus)
-bacteria are nitrogen-fixers-obtain N2 from soil & pass it on to plants
-bacteria break down organic molecules-oil, detergent, dead organisms
-bacteria help keep the poulation of harmful bacteria down (compete for space and food) - Harmful baceria
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Clostridium tetani:tetanus(paralysis)
Clostridium botulinum:botulism (food poisoning)
Yersinia pestis:bubanic plague (fleas, rats...human)
Borrelia burgdorferi:lyme disease(tick...human)
Mycobacterium:tuberculosis
Treponema pallidum-syphilis
Neisseria gonorrhoeae:gonorrhea
Cholera:spreads in H20
Streptococcus pneumoniae-pneumonia
Excherichia coli-E.Coli - Pathogenic
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disease-causeing
-toxic bacteria-producing poisons - Antibiotic resistance
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bacteria develop a resistance to bacteria when mutations in their DNA occur. Favorable mutations allow bacteria to survive exposure to antibiotics, & then pass that resistance on to other bacteria (of same or different species) by congugations.
Due to: overuse by doctors & agriculture
Antibiotic resistant bacteria include-gonorrhea, TB, starphoccues
Resistant to: tetracycline, penicillin, vancomycin