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38 Cards in this Set

  • Front
  • Back
-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
-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
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 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
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
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
Herpes type I-mucus membrane of lips
Herpes type II-genital area
HIV-T cells
Influenza-epithials in respiratory system
Rabies-nerve cells
Bacteria- bacteriophages -viruses that attack bacteria
some viruses are used to transfer genes from cells of on to cells of another species
Examples of initiators of cancer
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
Human Immunodecifiency virus(HIV)-causes AIDS
Herpes Simplex Type 2(HSV2)-genital herpes-lesions
HPV-genital warts
Other viral diseases
West Nile virus
Viral Classification
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...
-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
Acyclovir-for Herpes

Protease inhibitors-slows development of AIDS
-circular strands of RNA particles with no protein coat
-enter host cell, make more viroids
-attack plants
-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
-prokaryotes, live in extreme conditions(hot, cold, acidic, salty)
-still being discovered and classified
-some are very old (ancient)
-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:
-nutrient requirements
-method of locomotion
-colony growth patterns
-Gram Staining characteristics
Classificatino of bacteria is changing rapidly because...
-due to discovery of new organisms
-due to analysis of DNA and RNA
-new kingdoms being formed
Bacterial Shapes
rod-like - - bacillus
spherical - - coccus
corkscrew-shaped - - sprillum
Bacterial Locomotion
-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
-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
-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
-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
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
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
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
rod-shaped, anaerobic, produce methane(CH4)
-live in marshes, bottom of lakes
-require high concentrations of salt
-Great Salt Lake, Utah
-live and grow in hot(100 C), acidic (pH=1) environments
Bacterial Metabolism
-some are anaerobic/some are aerobic
-some are able to metabolize (methane, H, S, Fe, NH3)
blue/green bacteria that get energy through photosynthesis
Useful bacteria
-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
Clostridium tetani:tetanus(paralysis)
Clostridium botulinum:botulism (food poisoning)
Yersinia pestis:bubanic plague (fleas, rats...human)
Borrelia burgdorferi:lyme disease(tick...human)
Treponema pallidum-syphilis
Neisseria gonorrhoeae:gonorrhea
Cholera:spreads in H20
Streptococcus pneumoniae-pneumonia
Excherichia coli-E.Coli
-toxic bacteria-producing poisons
Antibiotic resistance
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