Micro Ch 13

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  1. How is a virus different from a bacterium
    • Virus: obligatory intracellular parasite 
    • bacteria: typical bacteria isnt a intracell parasite

    • virus: DNA or RNA no plasma membrane
    • bacteria: DNA and RNA with plasma membrane

    • virus: Dont make ATP, no ribosomes
    • bacteria: make ATP, ribosomes

    • virus: interferon sensitive
    • bacteria: antibiotic sensitive 

    virus: host depends on attachment and cell factors
  2. Can a virus replicate independently?

    Whats bigger a virus or bacterium?
    viruses cannot replicate independently, they need a host

    bacteria> virus
  3. What chemical and physical structures of both an envelope and non enveloped virus
    Both have a capsid ( protein coat)  made of capsomers that protect nucleic acids 

    • Enveloped virus: 
    •   chem- Capsid has a lipid, p, c over it 
    •   envelope has proteins picked by viral nucleic acid +host 
    •   physical- depends on the virus envelopes may or may not be covered in spikes ex. flu

    • Non eveloped virus:
    • -capsid has no envelope, and protects nucleic acids from nuclease enzymes ( which causes viruses to attach to susceptible host cells)
  4. What is the viral species, and how does it differ from bacterial species
    • viral species: viruses that share the same genetic info as the host 
    • - common name - subspecies # 

    • ex. family: herpesviridae
    •      genus: simple x virus 2 
    • human herpes virus 2 

    bacteria: genus, specific epiphet
  5. Describe how bacteriophages and animal viruses are grown
    A virus can't multiple outside a living host, but viruses can use bacteria as a host ( bacteriophages) 

    • bacteriophages: 
    • 1) bacteriophage + host+nutrient agar
    • 2) solidify 1 layer, each virus infects bacteria, multiples = hundreds of new viruses 
    • 3) multiple cycles, bacteria=destroyed = plaques ( each plaque is a virus) 

    • Animal virus
    • can be grown in living things ( embryonic egg) , innoculate living animal with virus 

    • Ex. embryonic eggs
    • 1) drill hole in shell, inject the virus
    • 2) vaccine can have egg protein
  6. 3 techniques used to identify viruses
    Cytopathic effects : structure change in host cells 

    Serological methods ex. western blot-- detect antibodies against the virus, use the antibodies to identify the virus in neutralized tests 

    - Nucleic acids ... RFLP, PCR
  7. Describe the lytic cycle of T-even bacteriophages
    Lytic cycle: ends with lysis  ( host cell death)

    Virus=large, complex, no envelope, head + tail 

    5 stages...

    • 1) Attachment: phage attaches by tail to host
    • 2) Penetration: injects DNA in bacteria to do this the tail first releases an enzyme ( phage lysozyme- which opens the cell wall)
    • 3) Biosynthesis: DNA in cytoplasm of host 
    • - host stops its own protein synth
    • -phage makes copies of DNA +protiens
    • 4) Maturation: bacteriophage DNA + Capsid=virons
    • 5)Release: phage lysozyme breaks bacterial cell wall to infect surrounding cells 

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  8. Describe the lytic and lysogenic cycles of bacteriophage lambda
    • ph 383-384 Unlike t cells, some cells don't cause cell death to the host when they multiple  
    • Ex.
    • 1)Ecoli is penetrated 
    • 2)The original linear phage of DNA forms a circle
    • 3a)Circle can multiple + transcribe
    • 4a)Leading to new phages being made and to cell lysis in the lytic cycle 

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  9. How do bacteriophages get nucleotides and amino acids if they dont have any metabolic enzymes?
    Bacteriophages propagate themselves by hijacking the metabolic enzymes of bacteria they infect and using amino acids and nucleotides already present in the cytoplasm
  10. Compare and contrast the multiplication cycle of DNA and RNA-containing animal viruses
    DNA-containing animal viruses......

    • 1) Attachment: Viruses attach to the cell membrane 
    • 2) Entry: Capsid enters by receptor-mediated endocytosis/fusion
    • 3)Uncoated: Once the viron is enclosed in the vesicle, the viral nucleic acid from its protein coat is separated by viral/host enzyme
    • 4)Biosynthesis: In nucelus the viral dna is released ,transcription and translation
    • 5) Maturation: the viral DNA and capsid proteins assemble to form complete viruses 
    • 6)Release: complete viruses are released from host cell 

    RNA-containing animal viruses 

    Mostly the same as DNA viruses, except that different mechanisms of mRNA formation occur different depending on the virus 

    - RNA viruses multiply in the cytoplasm ( instead of the nucleus) in the biosynthesis phase 

    - maturation release by budding ( enveloped viruses) or rupture

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  11. How is an RNA containing virus more efficient at infection and protein production than a DNA containing virus?
  12. What are the differences between a retrovirus and the other types of RNA viruses
    • Retrovirus: 
    • -viral RNA is transcribed to DNA, which can integrate into host DNA
    • ex. human t-lymphotropic virus HTLV
  13. How a virus can cause cancer by activating ocogenes?
    Cancer-causing alterations to cellular DNA affect parts of the genome called oncogenes.

    • Oncogenes can be activated by 
    • -mutagenic chemicals - radiation - oncoviruses

    - oncogenic viruses genetic material integrates into the hosts cells DNA and replicates along with the host cell's chromosome 

    transformed cells have increased growth, loss of contact inhibition, tumor specific transplant antigens ( t-antigen) causes abnormalities
  14. Acute, latent and persistant viral infection
    Latent: virus remains asymptomatic host cell for long periods ex. cold sore, shingles, herpes 

    Persistent: disease process occurs over a long period generally is fatal ex. measles 

    acute infection: rapid onset, short duration, host cells destroyed ex. influenza, cold , polio
  15. How can a protein be infectious?
    prions= infectious proteins 

    ex. mad cow disease, sheep scrapie, Creutzfeldt-Jakob disease 

    Inherited+ transmissible by ingestion, transplant, surgical instruments 

    Mammals make normal proteins called cellular PrP with alpha helix folding.

    Disease causing proteins called prion Prp is beta pleat folded.

    • If an abnormal prion protein PrpSC enters a cell it changes the normal prion protein to PRPSC = causing lots of abnormal PRPSC cells 
    • - not curable
  16. Which viral families use double-stranded DNA as their genetic info
    Non enveloped viruses 

    -  Adenoviridae ( respiratory infections in humans, tumors in animals) 

    - Poxviridae ex. orthopoxvirus ( cowpox, small pox

    • - herpesviridae ( simplevirus ( HHV-1, HHV-2) 
    • Cytomegalovirus ( HHV-5)
    • Kaposi sarcoma ( HHV-8)
    • some herpes viruses can remain latent in host cells
  17. Which viral families use +strand RNA as their genetic info
    Non enveloped viruses:

    • - Picornaviridae 
    • Ex. Enterovirus ( polio, coxsackievirus)
    •      Rhinovirus ( common cold)
    •      Hepatitis A 

    Enveloped Virus 

    • - Flaviviridae
    •       Ex. arbovirus ( replicates arthropods) yellow fever, dengue,west nile 
    • -Hep C
  18. Which viral families use -strand RNA as their genetic info
    • 1 RNA strand
    • -Lyssavirus ex. rabies ( cause numerous animal diseases)
    • -Filoviridae ex. filovirus ( enveloped helicle virus) , ebola, marburg 

    • Multiple RNA strands
    • -Orthomyxoviridae
    • enveloped spikes can agglutinate red blood cells ex. flu 
    • - influenza virus ( A, B)
    • -influenza c
  19. Which viral family turns its RNA genetic info into DNa
    • Single stranded RNA, 2 RNA strands == DNA
    • - use reverse transcriptase to produce DNA from a viral genome 

    • Retroviridae ex. lentivirus ( HIV) 
    • oncogenic viruses ( all RNA tumor viruses)

Card Set Information

Micro Ch 13
2016-10-11 02:52:26
Viruses,, Viroids, Prions
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