Viruses History (1)
Explain Smallpox & Flu pandemics
- caused by Variola
- killed 300 million
- changed many to christianity
- From Europe (Conquistadores: Pizarro & Cortes)
- expansion of afrian slaves bring yellow fever
- Mutation of flu
- Influenza - described by Hipocrates. Antigenic shift: major genetic change in H & N spike
- Spanish Flu - killed 50 million ppl. Dropped life expectancy by 12 years
Viruses History (2)
Who issolated a tobacco virus?
Contagium vivum fluidum/contagious fluid
Wendell Stanley isolated tobacco virus for Chemcial & Structural composition
Descibe a virus
What does living organisms consists of?
Virus are inert outside a cell. Has no cellular life
- Obligate intracellular parasite
- Has DNA or RNA
- Enclosed by envelope
- has spikes (receptors determine what to infect)
- most infects specific cells
- Family: Viridae (Retroviridae)
- Genus: Virus (Lentivirus)
- Subspecies designated by a number i.e. (HIV-1)
- metabolic process
What is phage?
Define Phage Therapy
Viruses that infect bacteria.
Receptor site is cell wall or Fimbraie or flagella
Potential candidate for disease treatment. Genetically manipulate to target specific cells i.e. tumors
How do viruses attach?
chemically interacts with a recptor site of host cell
Receptor site for Bacteriophage is cell wall or Fimbraie or flagella
Receptor site for Animal Virus is plasma membrane of host
What does it consist of?
Complex Viral Structure
Name the parts of the body
Viral enzyemes concerned entirely with replicating or processing nucleic acid
Must invade a host cell
Hijacks host cells
Assembles and bursts our of the cell
Describe the 2 types of multiplication process
2 types of multiplication
1) Lytic cycle: ends with lysis and death of host cell. Phage attaches by tail fiber
- Penetration: Lysozyme opens cell wall and tail sheath contracts and forces tail fiber and DNA into host cell.
- Biosynthesis: Production of virus DNA and proteins
- Maturation: Assembles virus particles
- Release: Virus lysozyme breaks thru cell wall
2) Lysogenic cycle: Ends with host cell remaining alive
- Prophage: inserted DNA (inactive)
- Lysogenic cell: Incorporates virus DNA into bacteria host DNA
- Sponaneous event or other stimulation occurs
- Phage is activated and iniates Lytic cycle (Biosynthesis > Maturation > Release)
Immune to reinfection by same phage
Phage conversion: exhibiting new properties, producing toxins
Specialized transduction: viruses transfering segments of DNA from one bacteria to another
Animal Virus Multiplication
Whats different about poliovirus
Similar to bacteriophage multiplication except
Entire virus enters host cells (Pinocytosis)
Attaches to protein and glycoprotein of plasma membrane
Attachment site is found over the entire surface of virus
Enveloped virus enters host cell via Fusion
After infusion, capsid is released into host cytoplasm (HIV)
- Attachment: virus attaches cell membrane
- Penetration: via endocytosis or fusion
- Uncoating: by virus or host enzymes. It uncoats viral nucleic acid via lysosomal enzymes of the host. (Except: polio. It uncoats itself during attachment).
- Biosynthesis: produces nucleic acid and proteins
- Maturation: Assembles nucleic acid and capsid proteins
- Release: via Budding (enveloped) or rupture (uneveloped)
Synthesize RNA from DNA via RNA Polymerase using DNA template
Synthesize DNA from RNA via reverse transcriptase using RNA template
Synthesize Polypeptides from mRNA templates
Biosynthesis of DNA Virus
DNA is synthesize in the nucleus
Viral capsid and proteins are synthesized in host cytoplasm then travels into the nucleus to assemble with the DNA
The complete virus is transported along the endoplasmic reticulum to the plasma membrane.
Attachment > Entry > uncoating > DNA released
Types - there are 2 types: single stranded and double stranded
Biosynthesis of Single Stranded RNA Virus
Sense strand (+) acts as mRNA produce (-) antisense strand
Antisense strand (-) acts as template to produce sense (+) strand
The 2 compliments each other.
Then maturation and then released.
Biosynthesis of Double Stranded RNA Virus
Both anti sense and sense strand
RNA virus that makes double stranded DNA via reverse transcriptase.
RNA uses reverse transcriptase molecule to make a strand of DNA in the cytoplasm.
The single stranded DNA is reversed transcribed again to produce double stranded DNA in the cytoplasm.
The Double stranded DNA then moves into the nucleus and attaches to host chromosomes: PROVIRUS
RNA polymerase makes mRNA which makes other components of the virus such as the envelope and proteins.
Then buds off.
Protease then helps rearrange the virion to infect