F.2 Flashcards
Life Characteristics (5)
- Metabolism
- Growth
- Responsiveness
- Control
- Organizational & Structural similarities: Genome + Barrier 4
is a virus alive? what does it do and doesn’t do?
no it is not alive:
-Does not respire
-Does not display irritability
-Does not grow*
-Does reproduce
-Adapt to new hosts
what does “bottom up” mean?
-simplest form capable of displaying the most essential attributes of an organism
* Replication + Adaptation
new definition of an organism
the unit element of a continuous lineage with an individual evolutionary history
life dependence of virus
-Cannot carry out metabolic activity
-Cannot reproduce independently
-No membrane bound organelles
-No lipid membrane*
-Do not grow in size or respond to direct environment
-Do not follow the Central Dogma
Typical Virus are:
-Sub-Microscopic
-Acellular (No organelles)
-Nucleic Acid content (Amount/Type)
-Barrier (Capsid enclosure)
-Infectious
-Intra- & Extra-cellular states
-Virus/Virion
states of viruses:
Extracellular (Virion):
* Possess a protein coat [capsid]: Capsid + Genome = Nucleocapsid
* Recognition for host: Infectious stage
* May possess a phospholipid cover [envelope]
Intracellular (Virus):
* No capsid present
* Replication stage
taxa for viruses
-Order (-virales): highest currently recognized.
-Family (-viridae)
-Subfamily (-virinae)
» Genus (-virus)
* Species/Specific epithet (e.g.: hanta virus)
taxonomic criteria for virus
GHP
- Genome Structure
- Host Organism(s)
- Particle Morphology
* Disease symptoms, antigenicity, protein profile, host range, etc. (familial if not generic level)
viral genome options:
content?
strand?
how many?
arrangement?
decodability?
-DNA or RNA (never both*): Content is low
-Single-stranded (ss) or Double-stranded (ds)
-Multiple vs. Single
-Arrangement: Linear Molecules, Circular Molecules
-Decodability: Positive Sense, Negative Sense
viral genome: decodability
Sense:
* Positive: Direct production of protein
Negative:
* Additional steps required to produce protein
* Usually complementary to template strand
what can viruses infect?
-all cellular organisms can be infected: all 5 kingdoms (all 3 domains)
-infection is based on complementarity: surface antigens (proteins, glycoproteins)
Virus families infecting two kingdoms of organisms are
-Bunyaviridae (animals and plants)
-Partitiviridae (plants and fungi)
-Reoviridae (animals and plants)
-Rhabdoviridae (animals and plants)
-Phycodnaviridae (protozoa and plants)
-Picornaviridae (plants and animals - tentative)
-Totiviridae (protozoa, fungi and insects- tentative)
viral morphology:
-Average bacterial range: 1-4μm, Visualized via Light Microscopy
-Viral size: 10nm («400nm)
capsid are:
-Virus/Virion: Nucleic Acid, Protein Coat (Capsid)
-Capsid:-
-Repetitive units of one or few proteins: Capsomeres
-Functions: Structural (Enclosure), Enzymatic
-Helical/Tube
-Spherical/Polyhedral
-Complex
-Binal (Phage)
envelope of virus
-Viral Membranes: Similar composition to cellular membrane “Enveloped viruses”
-Host-acquired: With (Enveloped), Without (Non-
enveloped or Naked)
-Viral protection mechanism
viral types (order)
-Ligamenvirales: infecting archaea
-Caudovirales: dsDNA bacteriophages
-Herpesvirales: large eukaryotic dsDNA viruses
-Ligamenvirales: dsDNA archaean viruses
-Mononegavirales: nonsegmented (-) strand ssRNA plant and animal viruses
-Nidovirales: (+) strand ssRNA viruses with vertebrate hosts
-Picornavirales: small (+) strand ssRNA viruses that infect a variety of plant, insect and animal hosts
-Tymovirales: (+) ssRNA viruses that infect plants
basic stages of virus
- Attachment: Locate and stick
- Entry: Getting in
- Synthesis: Making pieces
- Assembly: Putting it together
- Lysis: Getting out
lytic replication: prokaryotes
-Depend on hosts for life cycle:
* Enzymatic reaction: Ribosomal protein production, Replication mechanisms
-5 Characteristic steps:
* Attachment
* Entry
* Synthesis
* Assembly
* Lysis
bacteriophages: attachment
-Random collision of bacterium and phage
-Attraction between phage “tail fibers” and
proteins on bacterium: Cell wall, Flagellum, Pilus
bacteriophages: entry
-Overcoming of cell wall and membrane
-Penetration via:
* Perforation: Digestive enzymes (Lysozyme)
* Injection: Hollow tube
* Host override: Enzymes halt host metabolism
bacteriophages: entry expanded
Getting in:
-Variation on host type (Prokaryotic, Eukaryotic)
-Capsid morphology: Naked, Enveloped
Methods:
*Direct Penetration: Naked viruses, Perforation on cell barriers
*Membrane Fusion: Enveloped, Membrane layer
interaction
*Endocytosis: Enveloped, Host-cell eating triggered (Uncoating)
bacteriophages: synthesis
Overcoming of bacterial system:
*Entry of viral blueprint: DNA or RNA
*Entry of viral enzymes: Lysozyme destroys bacterial system, Polymerases replicate genome
*Bacterial system forced to produce viral system: Genome, Components
bacteriophages synthesis explained
Expression:
*Entry: Genetic Material, Accessory proteins
* Blueprint: May create needed proteins, Serves as template
*Proteins: May adapt genetic material, Replicate genetic material, Support in integration into host genome
Replication:
*Genetic material copied
*Genetic material adapted for copying
*Cell-type variation:
* Eukaryotes: Nuclear transcription & Assembly, Cytosolic Translation
*Prokaryotes: All cytosolic
