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Viral Structure & Function - Coggle Diagram
Viral Structure & Function
Defining Characteristics & History
Viruses
Obligatory intracellular parasites
small enough to pass through 0.2u filter
Contain nucleic acid (DNA or RNA) + capsid
some have an envelope
Difference from bacteria
No plasma
No binary fission
Cannot generate energy/proteins
Historical discoveries
1886: Adlof Mayer- Tabbaco Mosaic Disease (TMD) transmission
1892: Dimitri Iwanoski- "Filterable agent" concept
1901: Walter Reed- yellow Fever= first human viral disease, mosquito vector
Viral Structure & Genetics
Virion- complete, infectious viral particle
Capsid- Protein coat made of capsomeres
Envelope- Host membrane + viral proteins
Nonenveloped virus-Nucleic acid + capsid only
Spikes- Glycoprotein projections (e.g., influenza- hemmagglutation)
Types of Viral Material
ssDNA- Paraviridae (Parvirus)
dsDNA- Herpesviridae( Simpexvirus)
+ssRNA- Picornaviridae (Polio,Rhinovirus)
dsRNA- Reoviridae( Rotavirus)
Viral Morphology & Host Range
Morphology Types
Polyhedral - Icosahedra (Polio,Adenovirus)
Helical-Filovirus (Ebola), Lyssavirus(Rabies)
Icoshedral- Herpesviridae (Cold sores, Shingles)
Complex- dsDNA, enveloped, large (Bacteriophage)
Host Range
Most are species-specific
Few have broad host range
Attachment
Phages: Cell wall, fimbriae, flagella
Animal viruses: Plasma membrane proteins/glycoprotiens
Viral Replication
Entry (Animal viruses)- Pinocytosis or fusion
Uncoating- digestion of protein coat by lysosmal enzymes
DNA Virus Replication- Usually in nucleus
Exception: Pox Viruses (cytoplasm synthesis)
Lytic Cycle- T4 Phage (Virulent) Host cell dies
Lysogenic Cycle-Lambda phage (Temperate)
Phage DNA integrates-Prophage
Host survives; phage latent
Phage Conversion- Host gains new traits (e.g., diphtheria toxin gene)
Diseases & Special Viral mechanisms
yellow fever( Flavivirus, ssRNA, enveloped)
arthropod-bonrne
Sylvatic cycle: Mosquito
Urban cycle: Aedes aegypti-Humans
Prevention: Vaccine (17D strain), mosquito control
Influenza (orthomyxovirridae)
Genome: 8 RNA segments
H spikes- attachemnt
N spikes release from host
transmission: Aerosols
treatment:antivirals like osetamirvir
antigenic variation
shift: major recombination (swine infected with avian+ human flu)
drift: minor mutations (H/N spikes)- yearly vaccine updates
Latent Infections - reactive with stress(
Retrovirus (HIV)
has reverse transcriptase
viral TNA- dsDNA-integrates into host (Provirus)
Can stay latent and replicate with host DNA