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Viruses are?
- Non- Cellular
- Obligate intracellular parasites
- (have to)(inside)(cell) (kill/harm host cell)
- They have to get inside a cell to reproduce and then they kill or harm a host cell-usually.
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What is the Basic Cell Sturcture?
- Capsid (protein shell)
- Genetic Material
- Double-strand DNA, single strand DNA, D.S RNA, and S.S RNA.
- Some viruses: also have an envelope; envelope is a piece from previous hoat cell.
- (phospholipid bilayer with embedded proteins)
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What identifies a viruse?
- -enveloped or not
- -type of genetic material
- -size
- -capsid shape
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Types of Viruses? Determined by host cells
- 1. Bacterial viruses (bacteriophage)
- -infects bacterial cells--bacteria eater
- 2. Plant virsues
- -infects plants
- 3. Animal viruses
- -infects animals; including human pathogens
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Generalized Life Cycle? (5 steps)
- 1. Attachment (important step) to host cell
- viruses only attach to a host cell that only have appropriate receptors on cell surface.
- (This determines the virus specificity for a host cell) "What host can viruses infect?
- 2. Penetration/uncoating
- Virus get into host cell, and capsid is removed (genetic code is avaliable)
- Host phagocytosis virus
- -Virus injects nucleic acid
- -Viral envelope fuse with hos membrane
- 3. Replication (synthesis of viral parts)
- Using viral genetic code
- Use host cells materials (a.a, tRNA, etc) and ribosomes
- to make:
- -New viral genetic material
- -New viral proteins (for capsid or envelope-if appropriate)
- 4. Assembly
- Pieces of virus are put together to make new viruses. [virons]
- Place genetic material in capsid
- 5. Released from host
- Host cell lysis (dies)
- Virus can bud out of cell
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Specific viral life cycle?
- 1. Lytic cycle- see p. 7.6
- Cause lysis of host cell
- 2. Lysogenic cycle- see p. 7.7
- Sometimes host cell lysis; viral DNA become part of host DNA (genome)
- (1 and 2 happens in bacteria cells0
- 3. Retrovirus life cycle. see 7.8
- Happens in animals
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How virus help identify a bacteria?
- (Using viruses that do lytic cycle)
- A unkown bacteria is inoculated with a phage that kills E. coli, a phage that kills Salmonella, and a phage that kills Proteus.\
- Bacteria only dies with the phage that kills Salmonella, hence, the bacteria had the correct receptors for the phage to infect.
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What is retoviruses?
- Retroviruses (reverse)
- Perform the reverse of normal transcription.
- RNA make DNA by enzyme=reverse transcriptase
- Ex: H.I.V=Human ImmunoDeficiency Virus (Kills key immune system cells, patient becomes immundeficent)
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How to treat viral diseases?
- Some viral diseases can be trated with anti-viral medications.
- Many viruses-no safe treatment.
- Viral replication involves host material and host systems--if blocking viral replication, you can block these host processes.
- Vaccines- teaching the immune system to attack viruses.
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Prions- Proteins
- Cannot be destroyed ny standard sterization
- Cause [transmissible spongiform
- can be transmitted holes in brain
- encephalopathies]
- Brain damage
- Ex. mad cowl disease
- Prions protein- some a.a sequence as normal brain protiens fold differently.
- Reproduce-when a prion proteim bumbs into a normal protein, it causes that protein to fold like a prion protein.
- Transmission- ingestion of infected CNS (brain) tissue.
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